The Fertilisers (Sampling and Analysis) Regulations 1996

• (Note) Nitrobenzene or diethyl ether (especially the former) prevents the silver chloride from reacting with thiocyanate ions, thus a clear colour change is obtained.

Blank test

7.3

Carry out a blank test under the same conditions (omitting only the sample) and allow for this in the calculation of the final result.

Control test

7.4

Carry out the determination using 50ml (equivalent to 0.100g of chloride) of the potassium chloride solution (4.6).

EXPRESSION OF RESULT

8

Express the result of the analysis as a percentage of chloride contained in the sample as it has been received for analysis.

13a. — DETERMINATION OF FINENESS OF GRINDING — DRY METHOD

SCOPE

1

This method is for the determination of the fineness of grinding by the dry method.

FIELD OF APPLICATION

2

All fertilisers in Schedule 1 of the Fertilisers Regulations 1991 for which requirements are given of fineness of grinding using 0.630 mm and 0.160 mm sieves.

PRINCIPLE

3

By mechanical sieve shaking, the quantities of product with a granule size greater than 0.63 mm and those with a granule size between 0.16 mm and 0.63 mm are determined and the percentage of fineness of grinding is calculated.

APPARATUS

4

4.1

Mechanical sieve shaker.

4.2

Sieves with apertures of 0.160 mm and 0.630 mm respectively of standard ranges (diameter 20 cm, height 5 cm).

PROCEDURE

5

Weigh to the nearest 0.05 g, 50 g of the sample. Assemble the two sieves and the collecting container on the shaker (4.1), the sieve with the larger apertures being placed on top. Place the sample for analysis on the top. Sieve for ten minutes and remove the part collected on the bottom. Sieve again for one minute and check that the amount collected on the bottom during this time is not more than 250 mg. Repeat the process (for one minute each time) until the amount collected is less than 250 mg. Weigh the residual material on both sieves separately.

EXPRESSION OF RESULTS

6

Percentage of material passing sieve of 0.630 mm apertures = (50-M1) × 2

13b. — DETERMINATION OF FINENESS OF GRINDING OF SOFT NATURAL PHOSPHATES

SCOPE

1

This method is for determining the fineness of grinding of soft natural phosphates.

FIELD OF APPLICATION

2

Soft natural phosphates.

PRINCIPLE

3

For samples of fine particle size, agglomeration may occur thus making dry sieving difficult. For this reason, wet sieving is normally used.

REAGENTS Sodium hexametaphosphate solution, 1 g per 100 ml.

4

APPARATUS

5

5.1

Sieves with apertures of 0.063 mm and 0.125 mm respectively of standard ranges (diameter 20 cm, height 5 cm) and collecting containers.

5.2

Glass funnel of 20 cm diameter mounted on a stand.

5.3

Laboratory oven.

PROCEDURE

6

EXPRESSION OF RESULTS

7

REMARK

8

14. — METHODS OF ANALYSIS AND TEST PROCEDURES FOR AMMONIUM NITRATE FERTILISERS CONTAINING MORE THAN 28% NITROGEN BY WEIGHT

14a. — METHOD FOR THE APPLICATION OF THERMAL CYCLES

SCOPE

1

This method defines the procedure for the application of thermal cycles before carrying out the oil retention test on straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

FIELD OF APPLICATION

2

This procedure is for thermal cycling prior to determining the oil retention value of the fertiliser.

PRINCIPLE AND DEFINITION

3

Heat the sample in an Erlenmeyer flask by immersing the flask in a water bath at 50° C and maintain at this temperature for two hours (phase at 50° C). Then cool the flask in a water bath at 25° C and maintain at this temperature for two hours (phase at 25° C). The combination of the two phases, first at 50° C then at 25° C, forms one thermal cycle.

APPARATUS

4

Normal laboratory apparatus, in particular

4.1

Water baths thermostated at 25 (+1) and 50 (+1)° C respectively.

4.2

Erlenmeyer flasks with an individual capacity of 150 ml.

PROCEDURE

5

Place each test sample of 70(+5) grams into an Erlenmeyer flask which is then closed with a stopper. Place the flask in the 50° C water bath for 2 hours, then transfer to the 25° C bath for a further 2 hours. Transfer the flask back into 50° C water bath for a further 2 hours and then return to the 25° C bath.

14b. — DETERMINATION OF THE OIL RETENTION VALUE

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for the determination of the oil retention value of straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

DEFINITION

2

Oil retention value of a fertiliser: the quantity of oil retained by the fertiliser determined under the operating conditions specified and expressed as a percentage by mass.

PRINCIPLE

3

Total immersion of the test portion in gas oil for a specified period, followed by the draining away of surplus oil under specified conditions. Measurement of the increase in mass of the test portion.

REAGENT

4

Gas oil
Viscosity max:	5 mPas at 40° C
Density:	0.8 to 0.85 g/ml at 20° C
Sulfur content:	<1.0% (m/m)
Ash:<0.1% (m/m)

APPARATUS

5

5.1

Balance, capable of weighing to the nearest 0.01 gram.

5.2

Beakers, of capacity 500 ml.

5.3

Funnel, plastic, preferably with a cylindrical wall at the upper end, diameter approximately 200 mm.

5.4

Test sieve, aperture 0.5 mm, fitting into the funnel (5.3).

• (Note) The size of the funnel and sieve is such as to ensure that only a few granules lie one above another and the oil is able to drain away.

5.5

Filter paper, rapid filtering grade, creped, soft, weight 150 g/m2.

5.6

Absorbent tissue (laboratory grade).

PROCEDURE

6

6.1

Carry out two individual determinations in quick succession on separate portions of the same test sample.

6.2

Remove particles smaller than 0.5 mm using the test sieve (5.4). Weigh to the nearest 0.01 gram approximately 50 grams of the sample into the beaker (5.2). Add sufficient gas oil (Section 4) to cover the prills completely and stir carefully to ensure that the surfaces of all the prills are fully wetted. Cover the beaker with a watch glass and leave to stand for one hour at 25 (+2)° C.

6.3

Filter the entire contents of the beaker through the funnel (5.3) containing the test sieve (5.4). Allow the portion retained by the sieve to remain there for one hour so that most of the excess oil can drain away.

6.4

Lay two sheets of filter paper (5.5) (about 500 × 500mm) on top of each other on a smooth surface; fold the four edges of both filter papers upwards to a width of about 40 mm to prevent the prills from rolling away. Place two layers of absorbent tissue (5.6) in the centre of the filter papers. Pour the entire contents of the sieve (5.4) over the absorbent tissues and spread the prills evenly with a soft, flat brush. After two minutes lift one side of the tissues to transfer the prills to the filter papers beneath and spread them evenly over these with the brush. Lay another sheet of filter paper, similarly with its edges turned upward, on the sample and roll the prills between the filter papers with circular movements while exerting a little pressure. Pause after every eight circular movements to lift the opposite edges of the filter papers and return to the centre the prills that have rolled to the periphery. Keep to the following procedure: make four complete circular movements, first clockwise and then anticlockwise. Then roll the prills back to the centre as described above. This procedure to be carried out three times (24 circular movements, edges lifted twice). Carefully insert a new sheet of filter paper between the bottom sheet and the one above it and allow the prills to roll onto the new sheet by lifting the edges of the upper sheet. Cover the prills with a new sheet of filter paper and repeat the same procedure as described above. Immediately after rolling, pour the prills into a tared dish and reweigh to the nearest 0.01 gram to determine the mass of the gas oil retained.

Repeating the rolling procedure and reweighing.

6.5

If the mass of gas oil retained in the portion is found to be greater than 2.00 grams, place the portion on a fresh set of filter papers and repeat the rolling procedure, lifting the corners in accordance with Section 6.3 (two times eight circular movements, lifting once). Then reweigh the portion.

EXPRESSION OF RESULTS

7

Method of calculation and formula

7.1

The oil retention, from each determination (6.1) expressed as a percentage by mass of the sieved test portion, is given by the equation:

$$Oilretention=m2-m1m1×100$ where: ml is the mass, in grams, of the sieved test portion (6.2); m2 is the mass, in grams, of the test portion according to Section 6.4 or 6.5 respectively as the result of the last weighing. Take as the result the arithmetic mean of the two individual determinations.$

14c. — DETERMINATION OF COMBUSTIBLE INGREDIENTS

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for the determination of the combustible content of straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

PRINCIPLE

2

The carbon dioxide produced by inorganic fillers is removed in advance with an acid. The organic compounds are oxidised by means of a chromic acid/sulfuric acid mixture. Carbon dioxide formed is absorbed in a barium hydroxide solution. The precipitate is dissolved in a solution of hydrochloric acid and measured by back-titration with sodium hydroxide solution.

REAGENTS

3

3.1

Analytical-grade chromium VI oxide; CrVlO₃.

3.2

Sulfuric acid diluted to 60% by volume: pour 360 ml of water into a one litre beaker and carefully add 640 ml of sulfuric acid, density at 20° C p=1.83 g/ml.

3.3

Silver nitrate: 0.1 M solution.

3.4

Barium hydroxide:

3.5

Hydrochloric acid: 0.1 M standard solution.

3.6

Sodium hydroxide: 0.1 M standard solution.

3.7

Bromophenol blue: solution of 0.4 grams per litre in water.

3.8

Phenolphthalein: solution of 2 grams per litre in 60% by volume ethanol.

3.9

Soda lime: particle dimensions, about 1.0 to 1.6 mm.

3.10

Demineralised water, freshly boiled to remove carbon dioxide.

APPARATUS

4

Standard laboratory equipment, in particular:

4.1

filter crucible with a plate of sintered glass and a capacity of 15 ml, plate diameter: 20 mm, total height: 50 mm, porosity 4 (pore diameter from 5 to 15 μm);

4.2

Compressed nitrogen supply.

4.3

Apparatus made up of the following parts and assembled, if possible, by means of spherical ground joints (see Figure 9).

• (4.3.1) Absorption tube (A) about 200 mm long and 30 mm in diameter filled with soda lime (3.9) kept in place by fibreglass plugs.

• (4.3.2) 500 ml reaction flask (B) with side arm and a round bottom.

• (4.3.3) Vigreux fractioning column about 150 mm long (C').

• (4.3.4) Double-surface condenser (C), 200 mm long.

• (4.3.5) Drechsel bottle (D) acting as a trap for any excess acid which may distil over.

• (4.3.6) Ice bath (E) to cool the Drechsel bottle.

• (4.3.7) Two absorption vessels (F₁) and (F₂), 32 to 35 mm in diameter, the gas distributor of which comprises a 10 mm disc of low-porosity sintered glass.

• (4.3.8) Suction pump and suction regulating device (G) comprising a T-shaped glass piece inserted into the circuit, the free arm of which is connected to a fine capillary tube by a short rubber tube fitted with a screw clamp.

• Caution:

• the use of boiling chromic acid solution in an apparatus under reduced pressure is a hazardous operation and requires appropriate precautions.

PROCEDURE

5

Sample for analysis

5.1

Weigh approximately 10 grams of ammonium nitrate to the nearest 0.001 gram.

Removal of carbonates

5.2

Place the sample for analysis in the reaction flask (B). Add 100 ml of sulfuric acid (3.2). The prills dissolve in about 10 minutes at ambient temperature. Assemble the apparatus as indicated in the diagram: connect one end of the absorption tube (A) to the nitrogen source (4.2) via a non-return flow device containing 5 to 6 mm of mercury and the other end to the feed tube which enters the reaction flask. Place the Vigreux fractioning column (C') and the condenser (C) with cooling water supply in position. Adjust the nitrogen to provide a moderate flow through the solution, bring the solution to boiling point and heat for two minutes. At the end of this time there should be no more effervescence. If effervescence is seen, continue heating for 30 minutes. Allow the solution to cool for at least 20 minutes with the nitrogen flowing through it.

Oxidation and absorption

5.3

After withdrawing the nitrogen feed tube, rapidly introduce 20 grams of chromium trioxide (3.1) and 6 ml of silver nitrate solution (3.3) via the side arm of the reaction flask (B). Connect the apparatus to the suction pump and adjust the nitrogen flow so that a steady stream of gas bubbles passes through the sintered-glass absorbers (F₁) and (F₂).

Measurement of the carbonates originating from organic material

5.4

Add five drops of phenolphthalein (3.8) to the contents of the beaker. The solution becomes red in colour. Add hydrochloric acid (3.5) drop by drop until the pink colour just disappears. Stir the solution well in the crucible to check the pink colour does not reappear. Add five drops of bromophenol blue and titrate with hydrochloric acid until the solution turns yellow. Add a further 10 ml of hydrochloric acid.

BLANK TEST

6

Carry out a blank test following the same procedure, omitting the sample, and using the same quantities of all reagents.

EXPRESSION OF RESULTS

7

The content of combustible ingredients (C), expressed as carbon, as a percentage by mass of the sample, is given by the formula:

$$C%=0.06×V1-V2E$ where: E = the mass in grams of the test portion: V1 = the total volume in ml of 0.1 M hydrochloric acid added after the change in colour of the phenolphthalein; V2 = the volume in ml of the 0.1 M sodium hydroxide solution used in the titration.$

14d. — DETERMINATION OF THE pH VALUE

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for measuring the pH value of a solution of a straight ammonium nitrate fertiliser containing more than 28% nitrogen by weight.

PRINCIPLE

2

Measurement of the pH of an ammonium nitrate solution by means of a pH meter.

REAGENTS

3

Distilled or demineralised water, free from carbon dioxide.

Buffer solution, pH 6.88 at 20° C

3.1

Dissolve 3.40+0.01 grams of potassium dihydrogen orthophosphate (KH₂PO₄) in approximately 400 ml of water. Then dissolve 3.55+0.01 gram of disodium hydrogen orthophosphate (Na₂HPO₄) in approximately 400 ml of water. Transfer the two solutions without loss into a 1 litre graduated flask, make up to the mark and mix. Keep the solution in an airtight vessel.

Buffer solution, pH 4.00 at 20° C

3.2

Dissolve 10.21+0.01 grams of potassium hydrogen phthalate (KHC₈O₄H₄) in water, transfer without loss into a 1 litre standard flask, make up to the mark and mix.

3.3

Commercially available pH standard solutions may be used.

APPARATUS

4

pH meter, equipped with glass and calomel electrodes or equivalent, sensitivity of 0.05 pH unit.

PROCEDURES

5

5.1

Calibration of the pH meter

Determination

5.2

Pour 100.0 ml of water onto 10 (±0.01) grams of the sample in a 250 ml beaker. Remove the insolubles by filtering, decanting or centrifuging the liquid.

EXPRESSION OF RESULTS

6

Express the result in pH units, to the nearest 0.1 unit and state the temperature used.

14e. — DETERMINATION OF THE PARTICLE SIZE

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for the test sieving of straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

PRINCIPLE

2

The test sample is sieved on a nest of three sieves, either by hand or by mechanical means. The mass retained on each sieve is recorded and the percentage of material passing the required sieves is calculated.

APPARATUS

3

3.1

200 mm diameter woven-wire test sieves to BS 410 (1986) with apertures of 2.0 mm, 1.0 mm and 0.5 mm respectively of standard ranges. One lid and one receiver for these sieves.

3.2

Balance to weigh to 0.1 gram.

3.3

Mechanical sieve shaker (if available) capable of imparting both vertical and horizontal motion to the test sample.

PROCEDURE

4

4.1

The sample is divided representatively into portions of approximately 100 grams.

4.2

Weigh one of these portions to the nearest 0.1 gram.

4.3

Arrange the nest of sieves in ascending order (receiver, 0.5 mm, 1 mm, 2 mm) and place the weighed test portion on the top sieve. Fit the lid to the top of the nest of sieves.

4.4

Shake by hand or machine, imparting both a vertical and horizontal motion and, if by hand, tapping occasionally. Continue this process for 10 minutes or until the quantity passing through each sieve in one minute is less than 0.1 gram.

4.5

Remove the sieves from the nest in turn and collect the material retained, brush gently from the reverse side with a soft brush, if necessary.

4.6

Weigh the material retained on each sieve and that collected in the receiver, to the nearest 0.1 gram.

EVALUATION OF RESULTS

5

5.1

Convert the fraction masses to a percentage of the total of the fraction masses (not of the original charge).

5.2

At least two separate analyses should be carried out and the individual results for A should not differ by more than 1.0% absolute and for B by more than 1.5% absolute. Repeat the test if this is not the case.

EXPRESSION OF RESULTS

6

Report the mean of the two values for A on the one hand and for A+ B on the other hand.

14f. — DETERMINATION OF THE CHLORINE CONTENT (AS CHLORIDE ION)

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for the determination of the chlorine content (as chloride ion) of straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

PRINCIPLE

2

Chloride ions dissolved in water are determined by potentiometric titration with silver nitrate in an acidic medium.

REAGENTS

3

Distilled or demineralised water, free from chloride ions.

3.1

Acetone AR.

3.2

Concentrated nitric acid (density at 20°C p=1.40 g/ml).

3.3

Silver nitrate 0.1 M standard solution. Store this solution in a brown glass bottle.

3.4

Silver nitrate 0.004 M standard solution — prepare this solution at the time of use.

3.5

Potassium chloride 0.1 M standard reference solution. Weigh, to the nearest 0.1 mg, 3.7276 grams of analytical-grade potassium chloride, previously dried for one hour in an oven at 130° C and cooled in a desiccator to ambient temperature. Dissolve in a little water, transfer the solution without loss into a 500 ml standard flask, dilute to the mark and mix.

3.6

Potassium chloride 0.004 M standard reference solution — prepare this solution at the time of use.

APPARATUS

4

4.1

Potentiometer with silver indicating electrode and calomel reference electrode, sensitivity 2 mV, covering the range – 500 to +500 mV, or with silver and mercury (1) sulfate electrodes.

4.2

Bridge, containing a saturated potassium nitrate solution, connected to the calomel electrode (4.1), fitted at the ends with porous plugs. This bridge is not necessary if silver and mercury (1) sulfate electrodes are used.

4.3

etic stirrer, with a Teflon-coated rod.

4.4

Microburette with fine-pointed tip, graduated in 0.01 ml divisions.

PROCEDURE

5

Standardisation of the silver nitrate solution

5.1

Take 5.00 ml and 10.00 ml of the standard reference potassium chloride solution (3.6) and place in two low-form beakers of convenient capacity (for example 250 ml). Carry out the following titration of the contents of each beaker.

Blank test

5.2

Calculate the blank value using the equation below and take account thereof when calculating the final result.

Check test

5.3

The blank test can at the same time serve as a check that the apparatus is functioning satisfactorily and that the test procedure is being implemented correctly.

5.4

Determination

EXPRESSION OF RESULTS

6

Express the result of the analysis as the percentage of chlorine contained in the sample as received for analysis.

14g. — DETERMINATION OF COPPER

SCOPE AND FIELD OF APPLICATION

1

This method defines the procedure for the determination of the copper content of straight ammonium nitrate fertilisers containing more than 28% nitrogen by weight.

PRINCIPLE

2

The sample is dissolved in dilute hydrochloric acid and the copper content is determined by atomic absorption spectrometry.

REAGENTS

3

3.1

Hydrochloric acid (density at 20° C ρ = 1.18 g/ml).

3.2

Hydrochloric acid, 6 M solution.

3.3

Hydrochloric acid, 0.5 M solution.

3.4

Ammonium nitrate.

3.5

Hydrogen peroxide, 30%.

3.6

Copper solution[^f00016] (stock): weigh, to the nearest 0.001 gram, 1 gram of pure copper, dissolve in 25 ml of 6 M hydrochloric acid solution (3.2), add 5 ml of hydrogen peroxide (3.5) in portions and dilute to 1 litre with water. 1 ml of this solution contains 1,000 μg of copper (Cu).

• (3.6.1) Copper solution (dilute): dilute 10 ml of stock solution (3.6) to 100 ml with water and then dilute 10 ml of the resulting solution to 100 ml with water. 1 ml of the final dilution contains 10 μg of copper (Cu).

• Prepare this solution at the time of use.

APPARATUS

4

Atomic absorption spectrometer with a copper lamp (324.8 nm).

PROCEDURE

5

Preparation of the solution for analysis

5.1

Weigh 25 grams, to the nearest 0.001 gram, of the sample into a 400 ml beaker, add carefully 20 ml of hydrochloric acid (3.1) (there may be a vigorous reaction due to carbon dioxide formation). Add more hydrochloric acid, if necessary. When effervescence has stopped, evaporate to dryness on a steam bath, stirring occasionally with a glass rod. Add 15 ml 6 M hydrochloric acid solution (3.2) and 120 ml of water. Stir with the glass rod, which should be left in the beaker, and cover the beaker with a watch glass. Boil the solution gently until dissolution is complete and then cool.

Blank solution

5.2

Prepare a blank solution from which only the sample has been omitted and allow for this in the calculation of the final result.

Determination

5.3

• (5.3.1) Preparation of sample and blank test solutions

Dilute the sample solution (5.1) and the blank test solution (5.2) with 0.5 M hydrochloric acid solution (3.3) to a concentration of copper within the optimal measuring range of the spectrometer. Normally no dilution is needed.

• (5.3.2) Preparation of the calibration solutions

By diluting the standard solution (3.6.1) with 0.5 M hydrochloric acid solution (3.3), prepare at least five standard solutions corresponding to the optimal measuring range of the spectrometer (0 to 5.0 μg/l Cu). Before making up to the mark, add ammonium nitrate (3.4) to every solution to give a final concentration of 100 mg per ml.

Measurement

5.4

Set up the spectrometer (4) at a wavelength of 324.8 nm and use an oxidising air-acetylene flame. Spray, in triplicate, the calibration solutions (5.3.2), the sample solution and the blank solution (5.3.1), washing the instrument through with distilled water between each spraying. Plot the calibration curve using the mean absorbances of every standard used as the ordinates and the corresponding concentrations of copper in μg/ml as the abscissae.

EXPRESSION OF RESULTS

6

Calculate the copper content of the sample taking into account the weight of the test sample, the dilutions carried out in the course of the analysis and the value of the blank. Express the result as mg Cu/kg.

15. — EXTRACTION OF TOTAL CALCIUM, TOTAL MAGNESIUM, TOTAL SODIUM AND TOTAL SULFUR IN THE FORM OF SULFATES

SCOPE

1

This method is for the extraction of total calcium, total magnesium, total sodium and total sulfur present in the form of sulfates.

FIELD OF APPLICATION

2

This method applies to all fertilisers, for which a declaration of the total calcium, total magnesium, total sodium and total sulfur in the form of sulfates is required.

PRINCIPLE

3

Dissolution by boiling in dilute hydrochloric acid.

REAGENTS

4

4.1

Diluted hydrochloric acid; One volume of hydrochloric acid (p = 1.18g/ml) plus one volume of water.

APPARATUS

5

Electric hot plate with adjustable temperature.

PREPARATION OF THE SAMPLE

6

See method 1.

PROCEDURE

7

7.1

Test sample.

7.2

Preparation of the solution.

16. — EXTRACTION OF TOTAL SULFUR

SCOPE

1

This method is for the extraction of total sulfur contained in fertilisers in elemental form and/or in other chemical combinations.

FIELD OF APPLICATION

2

This method applies to all fertilisers for which a declaration of the total sulfur present in various forms (elemental, thiosulfate, sulfite and sulfate) is required.

PRINCIPLE

3

Elemental sulfur is converted in an alkaline medium into polysulfides and thiosulfate; these, together with any sulfites which may be present, are then oxidised with hydrogen peroxide. The various forms of sulfur are thus converted into sulfate which is determined by precipitation as barium sulfate (method 23).

REAGENTS

4

4.1

Diluted hydrochloric acid:

4.2

Sodium hydroxide solution, NaOH, 30% minimum (p = 1.33)

4.3

Hydrogen peroxide solution, 30% w/w.

4.4

Aqueous solution of barium chloride BaCl₂.2H₂O, 122 gram per litre.

APPARATUS

5

PREPARATION OF THE SAMPLE

6

See method 1.

PROCEDURE

7

7.1

Test sample.

7.2

Oxidation.

7.3

Preparation of the solution to be analysed.

17. — EXTRACTION OF WATER-SOLUBLE CALCIUM, MAGNESIUM, SODIUM AND SULFUR (IN THE FORM OF SULFATES)

SCOPE

1

This method is for the extraction of water-soluble calcium, magnesium, sodium and sulfur (in the form of sulfates), so that the same extract can be used to determine each nutrient required.

FIELD OF APPLICATION

2

This method applies solely to fertilisers for which a declaration of the water-soluble calcium, magnesium, sodium and sulfur (in the form of sulfates) is required.

PRINCIPLE

3

The nutrients are dissolved in boiling water.

REAGENTS

4

Distilled or demineralized water of equivalent quality.

APPARATUS

5

PREPARATION OF THE SAMPLE

6

See method 1.

PROCEDURE

7

7.1

Test sample.

• (a) Where fertilisers contain no sulfur or where they contain, at the same time, no more than 3% of sulfur (S) i.e. 7.5% SO3, and no more than 4% of calcium (Ca) i.e. 5.6% CaO, weigh out 5 g of fertiliser to within 1 mg.

• (b) Where fertilisers contain more than 3% of sulfur (S) and more than 4% of calcium (Ca), weigh out 1 g of fertiliser to within 1 mg.

Place the test sample in a 600 ml beaker.

7.2

Preparation of the solution.

18. — EXTRACTION OF WATER — SOLUBLE SULFUR

SCOPE

1

This method is for the extraction of water-soluble sulfur contained in fertilisers, in various forms.

FIELD OF APPLICATION

2

This method applies to all fertilisers for which a declaration of the water-soluble sulfur trioxide is required.

PRINCIPLE

3

Soluble forms of sulfur are dissolved in cold water and converted into sulfate by oxidation with hydrogen peroxide in an alkaline medium.

REAGENTS

4

4.1

Diluted hydrochloric acid:

APPARATUS

5

5.1

500 ml graduated Stohmann flask.

5.2

Rotary shaker, 30 to 40 turns per minute.

5.3

Electric hot plate with adjustable temperature.

PREPARATION OF THE SAMPLE

6

See method 1.

PROCEDURE

7

7.1

Test sample.

• (a) Where fertilisers contain a maximum of 3% of sulfur (S) i.e. 7.5% SO₃, together with a maximum of 4% of calcium (Ca) i.e. 5.6% CaO, weigh out 5 g of fertiliser to within 1 mg.

• (b) Where fertilisers contain more than 3% of sulfur (S) together with more than 4% of calcium (Ca), weigh out 1 g of fertiliser to within 1 mg.

Place the test sample in a 500 ml flask (5.1).

7.2

Preparation of the solution.

7.3

Oxidation of the aliquot portion to be analysed.

19. — EXTRACTION AND DETERMINATION OF ELEMENTAL SULFUR

WARNING

This method of analysis involves the use of carbon disulfide (CS2). Special safety measures must therefore be taken, in particular with regard to:

• the storage of CS2,

• protective equipment for staff,

• occupational hygiene,

• prevention of fires and explosions,

• disposal of the reagent.

This method requires highly skilled staff and a suitably equipped laboratory.

SCOPE

1

This method is for the extraction and determination of the elemental sulfur content of fertilisers.

FIELD OF APPLICATION

2

This method applies to all fertilisers for which a declaration of the total sulfur in elemental form is required.

PRINCIPLE

3

After the removal of soluble compounds, elemental sulfur is extracted by using carbon disulfide, followed by gravimetric determination of the sulfur extracted.

REAGENTS

4

Carbon disulfide.

APPARATUS

5

5.1

100 ml extraction flask with ground glass stopper.

5.2

Soxhlet apparatus.

5.3

Vacuum rotary evaporator.

5.4

Electric oven, fan assisted, set at 90+2° C.

5.5

Petri dishes, five to seven centimetres in diameter, not exceeding five centimetres in height.

5.6

Electric hot plate with adjustable temperature.

PREPARATION OF THE SAMPLE

6

See method 1.

PROCEDURE

7

7.1

Test sample. Weigh out 5 – 10 g of the sample to an accuracy of 1 mg and place in the thimble of the Soxhlet apparatus (5.2).

7.2

Extraction of the sulfur.

7.3

Determination of the purity of the elemental sulfur.

EXPRESSION OF RESULTS

8

The percentage elemental sulfur (S) content of the fertiliser is as follows:

$ImpureS(%)ofthefertiliser=P1-Pom×100$

20. — MANGANIMETRIC DETERMINATION OF EXTRACTED CALCIUM FOLLOWING PRECIPITATION IN THE FORM OF OXALATE

SCOPE

1

This method is for the determination of calcium in fertiliser extracts.

FIELD OF APPLICATION

2

This method applies to all fertilisers for which a declaration of the total and/or water-soluble calcium is required.

PRINCIPLE

3

Precipitation of the calcium contained in an aliquot portion of the extraction solution in the form of an oxalate, which is determined by titration using potassium permanganate.

REAGENTS

4

4.1

Diluted hydrochloric acid: One volume of hydrochloric acid (ρ = 1.18 g/ml) plus one volume of water.

4.2

1:10 dilute sulfuric acid:

4.3

1:1 dilute ammonia solution: One volume of ammonia (ρ = 0.88 g/ml) and one volume of water.

4.4

Saturated solution of ammonium oxalate [(NH₄)₂C₂O₄.H₂O] at ambient temperature (approximately 40 g per litre).

4.5

Citric acid solution, 30% (m/v).

4.6

Ammonium chloride solution, 5% (m/v).

4.7

Solution of bromothymol blue in 95% ethanol, 0.1% (m/v).

4.8

Solution of bromocresol green in 95% ethanol, 0.04% (m/v).

4.9

Standard solution of potassium permanganate, 0.02 M.

APPARATUS

5

5.1

Filter crucible with 5 to 20μ porosity sintered glass.

5.2

Hot water bath.

PREPARATION OF THE ALIQUOT PORTION TO BE ANALYSED

6

Using a pipette, take an aliquot portion of the extraction solution obtained by method 15 or 17, containing between 15 and 50 mg of Ca (= 21 to 70 mg of CaO). Let the volume of this aliquot be v₂. Pour into a 400 ml beaker. If necessary, neutralise (change of indicator (4.7) from green to blue) with a few drops of the ammonia solution (4.3).

PRECIPITATION OF THE CALCIUM OXALATE

7

Add approximately 100 ml of water. Bring to the boil, add 8 to 10 drops of indicator solution (4.8) and, slowly, 50 ml of the hot ammonium oxalate solution (4.4), stirring constantly. If a precipitate forms, dissolve by adding a few drops of hydrochloric acid (4.1). Neutralise very slowly with ammonia solution (4.3) while stirring continuously to a pH of 4.4 to 4.6 (change of indicator (4.8) from green to blue). Place the beaker in a boiling hot water bath (5.2) for approximately 30 minutes.

TITRATION OF THE OXALATE PRECIPITATE

8

Wash the beaker and crucible until the excess ammonium oxalate has been completely removed (this can be checked by the absence of chloride in the washing water). Place the crucible in the 400 ml beaker and dissolve the precipitate with 50 ml of hot sulfuric acid (4.2). Add water to the beaker in order to obtain a volume of approximately 100 ml. Bring to a temperature of 70 to 80° C and titrate drop by drop with the permanganate solution (4.9) until the pink colour lasts for a minute. Let this volume be n.

EXPRESSION OF RESULTS

9

The calcium (Ca) content of the fertiliser is as follows:

$$Ca(%)=n×0.2004×t0.02×v1v2×m$ Where: n = the volume of 0.2 M permanganate used, in millilitres, m = the mass of the test sample in grams, v₂ = the aliquot volume in millilitres, v₁ = the volume of the extraction solution in millilitres, t = the molarity of the permanganate solution in moles per litre. CaO(%) = Ca (%) × 1.400.$

21. — DETERMINATION OF MAGNESIUM BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method is for the determination of magnesium in fertiliser extracts.

FIELD OF APPLICATION

2

This method applies to all fertiliser extracts obtained by methods 15 and 17, for which a declaration of the total magnesium and/or water-soluble magnesium is required, with the exception of kieserite, magnesium sulfate, magnesium chloride solution and kieserite with potassium sulfate to which method 22 applies.

PRINCIPLE

3

Determination of magnesium by atomic absorption spectrometry after appropriate dilution of the extract.

REAGENTS

4

4.1

Hydrochloric acid, 1 M solution.

4.2

Hydrochloric acid, 0.5 M solution.

4.3

Standard solution of magnesium, 1.00 mg per ml.

• (4.3.1) Dissolve 1.013 g of magnesium sulfate (MgSO₄.7H₂O) in 0.5 M hydrochloric acid solution (4.2).

• or:

• (4.3.2) weigh out 1.658 g of magnesium oxide (MgO), previously ashed to remove all traces of carbonate. Place in a beaker with 100 ml of water and 120 ml of 1 M hydrochloric acid (4.1). When it has dissolved, transfer quantitatively into a 1 litre graduated flask. Make up to the volume and mix.

or:

• (4.3.3) Commercial standard solution.

The laboratory is responsible for testing such solutions.

4.4

Strontium chloride solution.

APPARATUS

5

5.1

Spectrometer fitted for atomic absorption, with a magnesium lamp, set at 285.2 nm.

5.2

Air-acetylene flame.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

See methods 15 and 17.

PROCEDURE

7

7.1

If the fertiliser has a declared magnesium (Mg) content of more than 6% (i.e. 10% as MgO), take 25 ml (V₁) of the extraction solution (6). Transfer into a 100 ml graduated flask, and make up to volume with water and mix. The solution factor is D₁ = 100/V₁.

7.2

Using a pipette, take 10 ml of the extraction solution (6) or the solution (7.1). Transfer into a 200 ml graduated flask. Make up to the volume with the 0.5 M hydrochloric acid solution (4.2) and mix. The dilution factor is 200/10.

7.3

Dilute this solution (7.2) with the 0.5 M hydrochloric acid solution (4.2) so as to obtain a concentration in the optimum working field of spectrometer (5.1). V₂ is the volume of the sample in 100 ml. The dilution factor is D₂ = 100/V₂.

7.4

Preparation of blank solution.

7.5

Preparation of calibration solutions.

7.6

Measurement.

EXPRESSION OF RESULTS

8

Calculate the amount of magnesium (Mg) or magnesium oxide (MgO) in the sample by reference to the calibration solutions and taking into consideration the blank.

22. — DETERMINATION OF MAGNESIUM BY COMPLEXOMETRY

SCOPE

1

This method is for the determination of magnesium in fertiliser extracts.

FIELD OF APPLICATION

2

This method applies to the determination of total magnesium and/or water-soluble magnesium in the following fertilisers:

• Straight nitrogenous fertilisers (calcium magnesium nitrate, magnesium sulphonitrate, nitrogenous fertiliser with magnesium) and straight potassic fertilisers (enriched kainite, potassium chloride containing magnesium, potassium sulfate containing magnesium salt), kieserite, magnesium sulfate, magnesium chloride solution, and kieserite with potassium sulfate.

PRINCIPLE

3

The magnesium is extracted by methods 15 and/or 17. First titration: with EDTA of Ca and Mg in the presence of Eriochrome black T. Second titration: with EDTA of Ca in the presence of calcein or of calcon carbonic acid. Determination of magnesium by difference.

REAGENTS

4

4.1

Standard 0.05 M solution of magnesium:

• (4.1.1) Dissolve 1.232 g of magnesium sulfate (MgSO4.7H2O) in the 0.5 M hydrochloric acid solution (4.11) and make up to 100 ml with the same acid.

or:

• (4.1.2) Weigh out 2.016 g of magnesium oxide, previously calcined to remove all traces of carbonation. Place it in a beaker with 100 ml of water.

Stir in approximately 120 ml of approximately 1 M hydrochloric acid (4.12).

• After dissolution, transfer quantitatively into a graduated 1 litre flask. Make up to volume and mix.

4.2

0.05 M solution of EDTA.

4.3

0.05 molar standard solution of calcium.

4.4

Calcein indicator.

4.5

Calcon carbonic acid indicator.

4.6

Eriochrome black — T indicator.

4.7

Potassium cyanide solution.

4.8

Solution of potassium hydroxide and potassium cyanide.

4.9

Buffer solution, pH 10.5.

4.10

Diluted hydrochloric acid:

4.11

Hydrochloric acid solution approximately 0.5 M.

4.12

Hydrochloric acid solution approximately 1 M.

4.13

Sodium hydroxide solution 5 M.

APPARATUS

5

5.1

Magnetic or mechanical stirrer.

5.2

pH meter.

CONTROL TEST

6

Carry out a determination on aliquot portions of solutions (4.1 and 4.3) such that the Ca/Mg ratio is approximately equal to that of the solutions to be analysed. To this end take (a) of standard solution (4.3) and (b – a) of standard solution (4.1). (a) and (b) are the volumes of EDTA solution in millilitres used in the two titrations performed on the solution to be analysed. This procedure is correct only if the solutions of EDTA, calcium and magnesium are exactly equivalent. If this is not the case, it is necessary to make corrections.

PREPARATION OF THE SOLUTION TO BE ANALYSED

7

See methods 15 and 17.

DETERMINATION

8

8.1

Aliquot portions to be taken.

8.2

Titration in the presence of Eriochrome black-T.

8.3

Titration in the presence of calcein or of calcon carbonic acid.

EXPRESSION OF RESULTS

9

For the EEC fertilisers to which the method is applicable (5 g of fertiliser in 500 ml of extract), the percentage content of the fertiliser is:

$MgO(%)inthefertiliser=(b-a)×TM$

REMARKS

10

10.1

The stoichiometric EDTA-metal ratio in the complexometric analyses is always 1:1 whatever the valency of the metal and in spite of the fact that EDTA is quadrivalent. The EDTA titration solution and the standard solutions will therefore be molar and not normal.

10.2

Complexometric indicators are often sensitive to air. The solution may lose colour during titration. In this case, one or two drops of indicator must be added. This is true particularly in the case of Eriochrome black-T and calcon carbonic acid.

10.3

The metal-indicator complexes are often relatively stable and it may take some time for the colour to change. The last drops of EDTA must therefore be added slowly and a drop of 0.05 molar solution of magnesium (4.1) or calcium (4.3) added to ensure that the colour change has not already taken place. This is particularly true in the case of the Eriochrome-magnesium complex.

10.4

The colour change of the indicator must not be observed vertically, but horizontally across the solution and the beaker must be placed against a white background in a well-lit position. The colour change of the indicator may also be observed easily by placing the beaker on frosted glass lit moderately from below (25 watt lamp).

10.5

This analysis requires a certain amount of experience. The task will involve, among other things, observing the colour changes of standard solutions 4.1 and 4.3. It is recommended that the determinations be carried out by the same laboratory chemist.

10.6

If an EDTA solution of guaranteed strength is used (Titrisol, Normex, for example) this may simplify the control of the equivalence of standard solutions 4.1, 4.2 and 4.3.

10.7

The solutions containing potassium cyanide must not be poured down the sink until the cyanide has been converted into a harmless compound, for example, by oxidation with sodium hypochlorite after having been made alkaline.

23. — DETERMINATION OF SULFATES

SCOPE

1

This method is for the determination of sulfur present in fertiliser extracts in the form of sulfates.

FIELD OF APPLICATION

2

This method applies to the determination of sulfates present in the extractions performed in methods 15, 16, 17 and 18.

PRINCIPLE

3

Gravimetric determination as barium sulfate.

REAGENTS

4

4.1

Diluted hydrochloric acid:

4.2

Barium chloride solution BaCl₂.2H₂O:122 grams per litre.

4.3

Silver nitrate solution: 5 grams per litre.

APPARATUS

5

5.1

Crucibles.

5.2

Hot water bath.

5.3

Drying oven set at 105° C ± 1° C.

5.4

Electric furnace set at 800° C ± 50° C.

PROCEDURE

6

6.1

Sampling of the solution.

6.2

Preparation of the precipitate.

6.3

Incineration and weighing of the precipitate.

EXPRESSION OF RESULTS

7

One mg of barium sulfate corresponds to 0.137 mg of S or to 0.343 mg of SO₃.

24. — DETERMINATION OF THE SODIUM EXTRACTED

SCOPE

1

This method is for the determination of sodium in fertiliser extracts.

FIELD OF APPLICATION

2

This method applies to fertilisers for which a declaration of sodium is required.

PRINCIPLE

3

Following suitable dilution of the extract obtained via method 15 and/or 17 the sodium content of the solution is determined by flame-emission spectrometry.

REAGENTS

4

4.1

Diluted hydrochloric acid:

4.2

Aluminium nitrate Al(NO₃)₃.9H₂O.

4.3

Caesium chloride, CsCl.

4.4

Anhydrous sodium chloride, NaCl.

4.5

Caesium chloride and aluminium nitrate solution.

4.6

Standard sodium solution of 1 mg/ml of Na.

APPARATUS

5

Spectrometer equipped for flame emission, set at 589.3 nm.

CALIBRATION SOLUTIONS

6

6.1

Pipette 10 ml of standard solution (4.6) into a 250 ml graduated flask. Make up to volume and mix. Concentration of solution: 40 μg/ml of Na.

6.2

Using a burette place 0, 5, 10, 15, 20, 25 ml of the intermediate solution (6.1) in 100 ml graduated flasks. Add 10 ml of the solution (4.5). Make up to volume and mix. Concentration of solutions: 0, 2, 4, 6, 8, 10 μg/ml of Na.

PREPARATION OF SOLUTIONS TO BE MEASURED

7

Depending upon the expected sodium content of the extraction solution as in method 15 or 17 (5 g of fertiliser in 500 ml), carry out the dilutions in accordance with the following table:

		Intermediate dilution	Intermediate dilution	Final dilution	Final dilution
Na2O (%)	Na (%)	Sample (ml) (v2)	Dilution to ml (v3)	Sample (ml) (v4)	Dilution to ml	Degree of dilution
3 – 5	2.2 – 3.7	10	50	10	100	50
5 – 10	3.7 – 7.4	10	100	10	100	100
10 – 20	7.4 – 15	10	100	5	100	200
20 – 38	15 – 28	5	100	5	100	400

DETERMINATION

8

Prepare the spectrometer (5) for the measurements at 589.3nm. Calibrate the instrument by measuring the response of the calibration solutions (6.2). Then adjust the sensitivity of the instrument to use its entire scale when the most concentrated calibration solution is used. Then measure the response of the sample solution to be analysed (7). Repeat this operation twice.

CALCULATION OF RESULTS

9

Draw a calibration curve by plotting the average response for each calibration solution along the ordinate and the corresponding concentrations, expressed in μg per ml on the abscissa. Determine from this the sodium concentration of the test solution. Calculate the quantity of sodium from the standard solutions taking account of the levels of dilution. Express the results as a percentage of the sample.

25. — TRACE ELEMENTS AT A CONCENTRATION LESS THAN 10%

25a. — EXTRACTION OF TOTAL TRACE ELEMENTS

SCOPE

1

This method defines the procedure for extracting the following trace elements: total boron, total cobalt, total copper, total iron, total manganese, total molybdenum and total zinc. The aim is to carry out the minimum number of extractions, making use wherever possible of the same extract to determine the total level of each of the trace elements listed above.

FIELD OF APPLICATION

2

This procedure concerns fertilisers containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It is applicable to each trace element the declared content of which is less than or equal to 10%.

PRINCIPLE

3

Dissolution in boiling dilute hydrochloric acid.

• (Note) The extraction is empirical and may not be quantitative depending on the product or the other constituents of the fertiliser. In particular, in the case of certain manganese oxides, the quantity extracted may be substantially smaller than the total quantity of manganese which the product contains. It is the responsibility of the fertiliser manufacturer to ensure that the declared content actually corresponds to the quantity extracted under the conditions pertaining to the method.

REAGENTS

4

4.1

Dilute hydrochloric acid (HCI) solution, about 6 M:

4.2

Concentrated ammonia solution (NH₄OH, p = 0.9g/ml)

APPARATUS

5

Electric hot plate with variable temperature control.

• (Note) Where the boron content of an extract is to be determined, do not use borosilicate glassware. As the method involves boiling, teflon or silica is preferable. Rinse the glassware thoroughly if it has been washed in detergents containing borates.

PREPARATION OF THE SAMPLE

6

See Method 1.

PROCEDURE

7

7.1

Test sample

7.2

Preparation of the solution

DETERMINATION

8

The determination of each trace element is to be carried out on the aliquot portions indicated in the method for each individual trace element.

25b. — EXTRACTION OF WATER-SOLUBLE TRACE ELEMENTS

SCOPE

1

This method defines the procedure for extracting water-soluble forms of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. The aim is to carry out the minimum number of extractions, making use wherever possible of the same extract to determine the level of each of the trace elements listed above.

FIELD OF APPLICATION

2

This procedure concerns fertilisers containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It is applicable to each trace element the declared content of which is less than or equal to 10%.

PRINCIPLE

3

The trace elements are extracted by shaking the fertiliser in water at 20° C±2°: C.

• (Note) The extraction is empirical and may or may not be quantitative.

REAGENTS

4

4.1

Dilute hydrochloric acid (HCI) solution, above 6 M:

APPARATUS

5

5.1

Rotary shaker set at about 35 to 40 rpm.

5.2

pH-meter.

• (Note) Where the boron content of the extract is to be determined, do not use borosilicate glassware. Teflon or silica is preferable for this extraction. Rinse the glassware thoroughly if it has been washed in detergents containing borates.

PREPARATION OF THE SAMPLE

6

See Method 1.

PROCEDURE

7

7.1

Test sample

7.2

Preparation of the solution

7.3

Preparation of the test solution

DETERMINATION

8

The determination of each trace element is carried out on the aliquot portions indicated in the method for each individual trace element.

25c. — REMOVAL OF ORGANIC COMPOUNDS FROM FERTILISER EXTRACTS

SCOPE

1

This method defines a procedure for removing organic compounds from fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble element is required.

• (Note) The presence of small quantities of organic matter usually does not affect determination by means of atomic absorption spectrometry.

PRINCIPLE

3

The organic compounds in an aliquot proportion of the extract are oxidised with hydrogen peroxide.

REAGENTS

4

4.1

Dilute hydrochloric acid (HCI) solution, about 0.5 M:

4.2

Hydrogen peroxide solution (30% H₂O₂ ρ = 1.11 g/ml), free from trace elements.

APPARATUS

5

Electric hot plate with variable temperature control.

PROCEDURE

6

Take 25 ml of the extract solution obtained by Method 25a or Method 25b and place in a 100 ml beaker. In the case of Method 25b add 5 ml of the dilute hydrochloric acid solution (4.1). Then add 5 ml of the hydrogen peroxide solution (4.2). Cover with a watch glass. Allow oxidation to occur at room temperature for about one hour, then bring gradually to boiling and boil for half an hour. If necessary, add a further 5 ml of the hydrogen peroxide to the solution once it has cooled. Then boil to remove the excess hydrogen peroxide. Allow to cool and transfer quantitatively to a 50 ml volumetric flask and make up to volume. Filter where necessary.

25d. — DETERMINATION OF TRACE ELEMENTS IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY (GENERAL PROCEDURE)

SCOPE

1

This method defines a general procedure for determining the levels of certain trace elements in fertiliser extracts by atomic absorption spectrometry.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertiliser extracts obtained by Methods 25a and 25b for which a declaration of total and/or water-soluble element is required.

PRINCIPLE

3

After the extract has been treated where necessary to reduce or eliminate interfering chemical species, the extract is diluted so that its concentration is in the optimum range of the spectrometer at a wave-length suitable for the trace element to be determined.

REAGENTS

4

4.1

Dilute hydrochloric acid solution (HCI), about 6 M:

4.2

Dilute hydrochloric acid solution (HCI), about 0.5 M:

4.3

Lanthanum salt solutions (10 g of La per litre).

4.4

Calibration solutions

APPARATUS

5

Atomic absorption spectrometer fitted with sources emitting radiation characteristic of the trace elements to be determined.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Preparation of extract solutions of the trace elements to be determined

6.2

Treatment of the test solution

PROCEDURE

7

7.1

Preparation of a blank solution

7.2

Preparation of calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

The percentage of trace element (E) in the fertiliser is equal to:

$E(%)=[(xs-xb)×V×D]/(M×104).$

25e. — DETERMINATION OF BORON IN FERTILISER EXTRACTS BY MEANS OF SPECTROMETRY WITH AZOMETHINE-H

SCOPE

1

This method describes a procedure for determining boron in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble boron is required.

PRINCIPLE

3

In an azomethine — H solution, borate ions form a yellow complex the concentration of which is determined by molecular absorption spectrometry at 410 nm. Interfering ions are masked with EDTA.

REAGENTS

4

4.1

EDTA buffer solution

4.2

Azomethine-H solution

4.3

Boron calibration solutions

• (4.3.1) Boron stock solution (100 μg/ml)

• Dissolve 0.5719 g of boric acid (H₃BO₃) in water in a 1,000 ml volumetric flask. Make up to volume with water and mix thoroughly. Transfer to a plastic bottle for storage in a refrigerator.

• (4.3.2) Boron working solution (10 μg/ml)

• Place 50 ml of stock solution (4.3.1) in a 500 ml volumetric flask. Make up to volume with water and mix thoroughly.

APPARATUS

5

Spectrometer fitted for molecular absorption with cells having a 10 mm optical path and set to a wavelength of 410 nm.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Preparation of the boron solution

6.2

Preparation of the test solution

6.3

Preparation of the correction solution.

PROCEDURE

7

7.1

Preparation of the blank solution

7.2

Preparation of the calibration solutions

7.3

Colour development

7.4

Determination

EXPRESSION OF RESULTS

8

Plot a calibration curve of the concentration of the calibration solutions (7.2) along the abscissa and the absorbance given by the spectrophotometer (7.4) along the ordinate.

25f. — DETERMINATION OF COBALT IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method describes a procedure for determining cobalt in fertilisers extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble cobalt is required.

PRINCIPLE

3

After suitable treatment and dilution of the extracts, the cobalt content is determined by atomic absorption spectrometry.

REAGENTS

4

4.1

Hydrochloric acid solution, about 6 M.

4.2

Hydrochloric acid solution, about 0.5 M.

4.3

Lanthanum salt solutions (10 g of La per litre)

4.4

Cobalt calibration solutions.

• (4.4.1) Cobalt stock solution (1,000 μg/ml)

In a 250 ml beaker, weigh to the nearest 0.1 mg, 1 g of cobalt, add 25 ml of 6 M hydrochloric acid (4.1) and heat on a hot plate until the cobalt is completely dissolved. When cool, transfer quantitatively to a 1,000 ml volumetric flask. Make up to volume with water and mix thoroughly.

• (4.4.2) Cobalt working solution (100 μg/ml)

Place 10 ml of the stock solution (4.4.1) in a 100 ml volumetric flask. Make up to volume with 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.

APPARATUS

5

Atomic absorption spectrometer: see Method 25d (5). The instrument must be equipped with a source of rays characteristic of cobalt (240.7 nm). The spectrometer must allow background correction to be made.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Cobalt extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of blank solution

7.2

Preparation of calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

See Method 25d (8).

25g. — DETERMINATION OF COPPER IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method describes a procedure for determining copper in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble copper is required.

PRINCIPLE

3

After suitable treatment and dilution of the extracts, the copper content is determined by atomic absorption spectrometry.

REAGENTS

4

4.1

Hydrochloric acid solution, about 6 M

4.2

Hydrochloric acid solution, about 0.5 M

4.3

Hydrogen peroxide solution (30% H₂O, p = 1.11 g/ml), free from trace elements.

4.4

Copper calibration solutions

• (4.4.1) Copper stock solution (1,000 μg/ml)

In a 250 ml beaker weigh to the nearest 0.1 mg, 1 g of copper, add 25 ml of 6M hydrochloric acid (4.1) add 5 ml hydrogen peroxide solution (4.3) and heat on a hotplate until the copper is completely dissolved. Transfer quantitatively to a 1 litre volumetric flask. Make up to volume with water and mix thoroughly.

• (4.4.2) Copper working solution (100 μg/ml)

Place 20 ml of the stock solution (4.4.1) in a 200 ml volumetric flask. Make up to volume with 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.

APPARATUS

5

Spectrometer equipped for atomic absorption: see Method 25.d (5). The instrument must be fitted with a source of rays characteristic of copper (324.8 nm).

PREPARATION FOR THE SOLUTION TO BE ANALYSED

6

6.1

Copper extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of blank solution

7.2

Preparation of calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

See Method 25d (8)

25h. — DETERMINATION OF IRON IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method describes a procedure for determining iron in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble iron is required.

PRINCIPLE

3

After suitable treatment and dilution of the extract, the iron content is determined by atomic absorption spectrometry.

REAGENTS

4

4.1

Hydrochloric acid solution, about 6M.

4.2

Hydrochloric acid solution, about 0.5 M

4.3

Hydrogen peroxide solution (30% H₂O₂ p = 1.11 g/ml) free from trace element.

4.4

Lanthanum salt solutions (10 g of La per litre)

4.5

Iron calibration solutions

• (4.5.1) Iron stock solution (1,000 μg/ml)

In a 500 ml beaker, weigh to the nearest 0.1 mg, 1 g of pure iron wire, add 200 ml of 6 M hydrochloric acid (4.1) and 15 ml of hydrogen peroxide solution (4.3). Heat on a hotplate until the iron is completely dissolved. When cool, transfer quantitatively to a 1 litre volumetric flask. Make up to volume with water and mix thoroughly.

• (4.5.2) Iron working solution (100 μg/ml)

Place 20 ml of the stock solution (4.5.1) in a 200 ml volumetric flask. Make up to volume with the 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.

APPARATUS

5

Atomic absorption spectrometer: see Method 25d (5). The instrument must be fitted with a source of rays characteristic of iron (248.3 nm).

PREPARATION FOR THE SOLUTION TO BE ANALYSED

6

6.1

Iron extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of blank solution

7.2

Preparation of calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

See Method 25d (8).

25i — DETERMINATION OF MANGANESE IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method describes a procedure for determining manganese in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble manganese is required.

PRINCIPLE

3

After suitable treatment and dilution of the extracts, the manganese level is determined by atomic absorption spectrometry.

REAGENTS

4

4.1

Hydrochloric acid solution, about 6 M

4.2

Hydrochloric acid solution, about 0.5 M

4.3

Lanthanum salt solutions (10 g of La per litre)

4.4

Manganese calibration solutions

• (4.4.1) Manganese stock solution (1,000 μg/ml)

In a 250 ml beaker, weigh to the nearest 0.1 mg, 1 g of manganese, add 25 ml of 6 M hydrochloric acid solution (4.1). Heat on a hotplate until the manganese is completely dissolved. When cool, transfer quantitatively to a 1,000 ml volumetric flask. Make up to volume with water and mix thoroughly.

• (4.4.2) Manganese working solution (100 μg/ml)

Place 20 ml of the stock solution (4.4.1) in a 200 ml volumetric flask. Make up to volume with the 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.

APPARATUS

5

Atomic absorption spectrometer: see Method 25d (5). The apparatus must be fitted with a source of rays characteristic of manganese (279.6 nm).

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Manganese extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of the blank solution

7.2

Preparation of the calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

See Method 25d (8).

25j. — DETERMINATION OF MOLYBDENUM IN FERTILISER EXTRACTS BY SPECTROMETRY OF A COMPLEX WITH AMMONIUM THIOCYANATE

SCOPE

1

This method describes a procedure for determining molybdenum in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble molybdenum is required.

PRINCIPLE

3

Molybdenum(v) forms a complex [MoO(SCN)5] – – in an acid medium with SCN – ions. The complex is extracted with n-butyl acetate. Interfering ions such as those of iron remain in the aqueous phase. The yellow-orange colour is determined by molecular absorption spectrometry at 470 nm.

REAGENTS

4

4.1

Dilute hydrochloric acid solution (HCI), about 6 M

4.2

Copper solution (70 mg/l) in 1.5 M hydrochloric acid

4.3

Ascorbic acid solution (50 g/l)

4.4

n-butyl acetate

4.5

Ammonium thiocyanate solution, 0.2 M

4.6

Stannous chloride solution (50 g/l) in 2 M hydrochloric acid

4.7

Molybdenum calibration solutions

• (4.7.1) Molybdenum stock solution (500 μg/ml)

Dissolve 0.920 g of ammonium molybdate [(NH₄)6 Mo₇O₂4.4H₂O] weighed to within 0.1 mg in the 6 M hydrochloric acid (4.1) in a 1 litre volumetric flask. Make up to volume with that solution and mix thoroughly.

• (4.7.2) Molybdenum intermediate solution (25 μg/ml)

Place 25 ml of the stock solution (4.7.1) in a 500 ml volumetric flask. Make up to volume with 6 M hydrochloric acid (4.1) and mix thoroughly.

• (4.7.3) Molybdenum working solution (2.5 μg/ml)

Place 10 ml of the intermediate solution (4.7.2) in a 100 ml volumetric flask. Make up to volume with 6 M hydrochloric acid (4.1) and mix thoroughly.

APPARATUS

5

5.1

Spectrometer fitted for molecular absorption with cells having a 20 mm optical path and set to a wavelength of 470 nm.

5.2

200 or 250 ml separating funnels.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Molybdenum extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of the blank solution

7.2

Preparation of the series of calibration solutions

7.3

Development and separation of the complex

7.4

Determination

EXPRESSION OF RESULTS

8

Construct the calibration curve by plotting the corresponding masses of molybdenum in the calibration solutions (7.2) expressed in μg along the abscissa and the corresponding values of the absorbencies (7.4) given by the spectrometer reading along the ordinate.

25k. — DETERMINATION OF ZINC IN FERTILISER EXTRACTS BY ATOMIC ABSORPTION SPECTROMETRY

SCOPE

1

This method describes a procedure for determining zinc in fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 25a and 25b for which a declaration of total and/or water-soluble zinc is required.

PRINCIPLE

3

After suitable treatment and dilution of the extracts, the zinc level is determined by atomic absorption spectrometry.

REAGENTS

4

4.1

Hydrochloric acid solution, about 6 M

4.2

Hydrochloric acid solution, about 0.5 M

4.3

Lanthanum salt solutions (10 g of La per litre)

4.4

Zinc calibration solutions

• (4.4.1) Zinc stock solution (1,000 μg/ml)

In a 1 litre volumetric flask dissolve 1 g of zinc powder or flakes weighed to within 0.1 mg in 25 ml of 6 M hydrochloric acid (4.1). When completely dissolved, make up to volume with water and mix thoroughly.

• (4.4.2) Zinc working solutions (100 μg/ml)

Place 20 ml of the stock solution, (4.4.1) in a 200 ml volumetric flask. Make up to volume with the 0.5 M hydrochloric acid solution (4.2) and mix thoroughly.

APPARATUS

5

Atomic absorption spectrometer: See Method 25d (5). The apparatus must be fitted with a source of rays characteristic of zinc (213.8 nm). The spectrometer must allow background correction to be made.

PREPARATION OF THE SOLUTION TO BE ANALYSED

6

6.1

Zinc extract solution

6.2

Preparation of the test solution

PROCEDURE

7

7.1

Preparation of the blank solution

7.2

Preparation of the calibration solutions

7.3

Determination

EXPRESSION OF RESULTS

8

See Method 25d (8).

26. — TRACE ELEMENTS AT A CONCENTRATION GREATER THAN 10%

26a. — EXTRACTION OF TOTAL TRACE ELEMENTS

SCOPE

1

This method defines the procedure for extracting the following trace elements: total boron, total cobalt, total copper, total iron, total manganese, total molybdenum and total zinc. The aim is to carry out the minimum number of extractions, making use wherever possible of the same extract to determine the total level of each of the trace elements listed above.

FIELD OF APPLICATION

2

This procedure concerns fertilisers containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It is applicable to each trace element, the declared content of which is more than 10%.

PRINCIPLE

3

Dissolution in boiling diluted hydrochloric acid.

• (Note) The extraction is empirical and may not be quantitative depending on the product or the other constituents of the fertiliser. In particular, in the case of certain manganese oxides, the quantity extracted may be substantially smaller than the total quantity of manganese which the product contains. It is the responsibility of the fertiliser manufacturers to ensure that the declared content actually corresponds to the quantity extracted under the conditions pertaining to the method.

REAGENTS

4

4.1

Diluted hydrochloric acid (HCI) solution, about 6M

4.2

Concentrated ammonia solution (NH₄OH, p = 0.9 g/ml)

APPARATUS

5

5.1

Electric hotplate with variable temperature control.

5.2

pH meter

• (Note) Where the boron content of an extract is to be determined, do not use borosilicate glassware. As the method involves boiling, teflon or silica is preferable. Rinse the glassware thoroughly if it has been washed in detergents containing borates.

PREPARATION OF THE SAMPLE

6

See Method 1.

PROCEDURE

7

7.1

Test sample

7.2

Preparation of the solution

DETERMINATION

8

The determination of each trace element is to be carried out on the aliquot portions indicated in the method for each individual trace element.

26b. — EXTRACTION OF WATER — SOLUBLE TRACE ELEMENTS

SCOPE

1

This method defines the procedure for extracting water-soluble forms of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. The aim is to carry out the minimum number of extractions, making use wherever possible of the same extract to determine the level of each of the elements listed above.

FIELD OF APPLICATION

2

This procedure concerns fertilisers containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It is applicable to each trace element, the declared content of which is more than 10%.

PRINCIPLE

3

The trace elements are extracted by shaking the fertiliser in water at 20±°C.

• (Note) The extraction is empirical and may not be quantitative.

REAGENTS

4

4.1

Diluted hydrochloric acid (HCI) solution, about 6 M

APPARATUS

5

5.1

Rotary shaker set at about 35 to 40 rpm.

• (Note) Where the boron content of the extract is to be determined, do not use borosilicate glassware. Teflon or silica is preferable for this extraction. Rinse the glassware thoroughly if it has been washed in detergents containing borates.

PREPARATION OF THE SAMPLE

6

See Method 1.

PROCEDURE

7

7.1

Test sample

7.2

Preparation of the solution

7.3

Preparation of the test solution

DETERMINATION

8

The determination of each trace element is carried out on the aliquot portions indicated in the method for each individual trace element.

26c. — REMOVAL OF ORGANIC COMPOUNDS FROM FERTILISER EXTRACTS

SCOPE

1

This method defines a procedure for removing organic compounds from fertiliser extracts.

FIELD OF APPLICATION

2

This procedure is applicable to analysing samples of fertilisers extracted by Methods 26a and 26b for which a declaration of total and/or water — soluble element is required.

• (Note) The presence of small quantities of organic matter usually does not affect determinations by means of atomic absorption spectrometry.

PRINCIPLE

3

The organic compounds in an aliquot portion of the extract are oxidized with hydrogen peroxide.

REAGENTS

4

4.1

Diluted hydrochloric acid solution, about 0.5 M

4.2

Hydrogen peroxide solution (30% H₂O₂, p = 1.11 g/ml), free from trace elements.

APPARATUS

5

Electric hotplate with variable temperature control.

PROCEDURE

6