Key Benefits:
The full integration of Spain into the European Community requires the harmonisation of national legislation with Community legislation.
Consequently, it is necessary to transpose Directive 95 /8/EC of the Commission of 10 April on methods of analysis of fertilizers, which involves the incorporation into the internal rules of new Community methods which to check their quality and composition conditions and to remove technical barriers to trade in the sector. The new methods are to be added to the official methods already in force, approved by the Orders of 30 November 1976, 31 July 1979, 17 September 1981, 1 December 1981 and 18 July 1989 and the Royal Decrees 1163/1991 of 22 July and 2490/1994 of 23 December.
The content of this standard is given in accordance with the provisions of Article 40.2 of Law 14/1986 of 25 April, General of Health, and of Article 149.1.13. and 16. of the Constitution, concerning the bases and coordination of the general planning of economic activity and the general foundations and coordination of health.
In the proceedings of this Royal Decree, the entities and organizations affected by it have been consulted and the report of the Inter-Ministerial Commission for Food Management has been issued.
In its virtue, on the proposal of the Ministers of Agriculture, Fisheries and Food, of Economy and Finance, of Industry and Energy, of Health and Consumer Affairs and of Trade and Tourism, in agreement with the State Council, and after deliberation of the Council of Ministers at its meeting on 28 March 1996,
D I S P O N G O:
Article 1. Object.
The fertilizer analysis methods set out in the Annex are approved as official.
Article 2. Supposed of non-existence of official methods.
When there are no official methods for certain fertilizer analyses, and until approved, those established in existing national standards or those international methods of recognition may be used. solvency.
Single additional disposition. Basic character.
The provisions of this Royal Decree have the character of basic State legislation under the provisions of Article 40.2 of Law 14/1986 of
25 April, General of Health, and article 149.1.13. and 16. of the Constitution, relating to the bases and coordination of the general planning of economic activity and the bases and general coordination of health.
Final disposition first. Powers of development.
the Ministers for Agriculture, Fisheries and Food, Economic and Finance, Industry and Energy, Health and Consumer Affairs and Trade and Tourism are empowered to adopt the provisions of this Regulation. necessary for the fulfilment and application of the provisions of this Royal Decree.
Final disposition second. Entry into force.
This Royal Decree shall enter into force on the day following that of its publication in the "Official Gazette of the State".
Dado en Madrid a 28 de marzo de 1996.
JOHN CARLOS R.
The Minister of the Presidency,
ALFREDO PEREZ RUBALCABA
A N E X O
INDEX
22 (b). Quantitative determination of boron in the extracts of fertilizers of contents greater than 10 per 100 per acimetry.
23 (e). Trace elements in contents greater than 10 per 100.
23 (f). Extraction of water-soluble oligoelements.
23 (g). Elimination of organic compounds in fertilizer extracts in contents greater than 10 per 100.
23 (h). Quantitative determination of trace elements in contents greater than 10 per 100 in the extracts of fertilizers by atomic absorption spectrometry (general method).
29 (b). Quantitative determination of zinc in contents greater than 10 per 100 in the extracts of fertilizers by atomic absorption spectrometry.
30 (c). Quantitative determination of copper in fertilizer extracts in contents greater than 10 per 100 by volume.
32 (b). Quantitative determination of iron in fertilizer extracts in contents greater than 10 per 100 by atomic absorption spectrometry.
33 (b). Quantitative determination of manganese in contents greater than 10 per 100 in the extracts of fertilizers by valuation as permanganate.
35 (b). Quantitative determination of molybdenum in contents greater than 10 per 100 in the extracts of fertilizers by gravimetry with 8-hydroxyquinoline.
37 (b). Quantitative determination of cobalt in the extracts of fertilizers of contents greater than 10 per 100 by gravimetry with 1-nitroso-2-naphthol.
I. METHOD 22 (b)
22 (b) Quantitative determination of boron in the fertilizer extracts of contents greater than 10 per 100 per acidetry.
22 (b) .1 Principle.
A method for the determination of boron in fertilizer extracts is described herein.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f), for which the Order of 14 June 1991, on fertilizers and related products, provides for the declaration of total boron content and/or water soluble boron content.
The borate ion forms with the mannitol a manitobboric complex according to the following reaction:
CH (OH) + HBO 1 CHOB + HO
The complex is valued with a sodium hydroxide solution up to a pH of 6.3.
22 (b) .2 Material and apparatus.
22 (b) .2.1 pHmeter with glass electrode
22 (b) .2.2 Magnetic Agitator
22 (b) .2.3 Vase of 400 ml precipitates with teflon bar.
22 (b) .3 Reassets.
22 (b) .3.1 methyl red indicator solution. In a 100 ml graduated flask, dissolve 0,1 g of methyl red (CHNO) in 50 ml of ethanol at 95 per 100. Make up with water. Homogenize.
22 (b) .3.2 Diluted hydrochloric acid solution, approximately 0.5 M. Mix a volume of hydrochloric acid (HCl, d = 1,18 g/ml) and 20 volumes of water.
22 (b) .3.3 Sodium hydroxide solution, approximately 0.5 M. It must be free of carbon dioxide. In a 1 litre graduated flask containing about 800 ml of boiled water, dissolve 20 g of sodium hydroxide (NaOH) in lentils. When the solution has cooled, make up with boiled water. Homogenize.
22 (b) .3.4 Sodium hydroxide pattern solution, approximately 0.025 M. It must be free of carbon dioxide. Dilute the sodium hydroxide solution 0.5 M (22 (b) .3.3) with boiled water and homogenise 20 times. The value expressed in B shall be determined (see paragraph 22 (b) .4.4).
22 (b) .3.5 Boron calibration solution (100 lg/ml B). In a 1,000 ml volumetric flask dissolve with water 0,5719 g of boric acid (HBO), weighed with a precision of 0,1 mg. Make up with water and homogenise. Move to a plastic bottle to store in the refrigerator.
22 (b) .3.6 D-mannitol (CHO) powder
22 (b) .3.7 Sodium chloride (NaCl).
22 (b) .4 Procedure.
22 (b) .4.1 Preparing the problem solution. Dissolution of boron. See methods 23 (e) and 23 (f) and, where appropriate, 23 (g).
22 (b) .4.2 Test. In the 400 ml beaker (23 (b) .2.3), insert an aliquot (a) taken from the extract (22 (b) .4.1) and contain between 2 and 4 mg boron (B). Add 150 ml of water.
Add some drops of the methyl red indicator solution (22 (b) .3.1).
In case of extraction by method 23 (f) acidify by adding hydrochloric acid 0,5 M (22 (b) .3.2) until the indicator turns and then add an excess of 0.5 ml of 0,5 M hydrochloric acid (22 (b) .3.2). Add 3 g of sodium chloride (22 (b) .3.7) and bring to the boil to remove carbon dioxide. Leave to cool. Put the beaker in the magnetic agitator (22 (b) .2.2) and insert into it the electrodes of the pHmeter (22 (b) .2.1) which will have been calibrated before. Adjust the pH to 6.3 exactly, first with the sodium hydroxide solution 0.5 M and then with the solution 0.025 M. Add 20 g of D-mannitol (22 (b) .3.6), dissolve completely and homogenize. Titrate with the sodium hydroxide solution 0.025 M (22 (b) .3.4) until reaching the pH of 6.3 (stability of at least 1 minute).
We will call X to the required volume.
22 (b) .4.3 Blank test. Run a blank test under the same conditions from the dissolution and omit only the fertilizer. We will call X to the required volume.
22 (b) .4.4 Value in boron (B) of sodium hydroxide solution (22 (b) .3.4). Take with a pipette 20 ml (equivalent to 2.0 mg boron (B)) of the calibration solution (22 (b) .3.5) and pass them to a 400 ml beaker; add a few drops of the methyl red solution (22 (b) .3.1). Add 3 g of sodium chloride (22 (b) .3.7) and hydrochloric acid solution (22 (b) .3.2) until the indicator solution turns (22 (b) .3.1). Complete the volume up to approximately 150 ml and slowly bring to the boil to remove the carbon dioxide. Leave to cool. Put the beaker in the magnetic agitator (22 (b) .2.2) and insert the electrodes of the pHmeter (22 (b) .2.1) into it, which will have been calibrated before. Adjust the pH to 6.3 exactly, first with the sodium hydroxide solution 0.5 M and then with the solution 0.025 M. Add 20 g of D-mannitol (22 (b) .3.6) completely dissolve and homogenize. Titrate with the sodium hydroxide solution 0.025 M (22 (b) .3.4) until reaching the pH of 6.3 (stability of at least 1 minute). We will call V to the required volume.
Perform a blank test in the same way, replacing the calibration solution with 20 ml of water. We will call V to the required volume.
The equivalence in boron (F) of the NaOH-rated solution (22 (b) .3.4) is as follows:
F (in mg/ml) = 2/(V-V)
Correspondence of 1 ml of sodium hydroxide solution exactly 0.025 M is 0.27025 mg of B.
22 (b) .5 Calculations.
The percentage of boron (B) of the credit is:
B (%) = (X-X) X F X V
10 X to X M
Being:
B (%)
= the percentage in boron of the fertilizer.
X
= the volume of the sodium hydroxide solution 0.025 M (22 (b) .3.4) required in the test (22 (b) .4.2), in ml.
X
= the volume of the sodium hydroxide solution 0.025 M (22 (b) .3.4) required in the blank test (22 (b) .4.3), in ml.
F
= the equivalence in boron (B) of the sodium hydroxide solution 0.025 M (22 (b) .3.4) in mg/ml.
V
= the volume of the extract obtained by method 23 (e) or 23 (f) in ml.
a
= the volume of the aliquot (22 (b) .4.2).
M
= the mass of the fertilizer sample taken according to method 23 (e) or 23 (f), in grams.
22 (b) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.5.
II. METHOD 23 (e)
23 (e) Oligoelements in contents greater than 10 per 100
Extracting the total oligoelements
23 (e) .1 Principle.
Dissolution in diluted and boiling hydrochloric acid.
Note: The extraction is empirical and may not be quantitative, depending on the product or other components of the fertilizer. In particular, in the case of certain manganese oxides, the quantities extracted may be much lower than the whole of the manganese contained in the product. It is the responsibility of the fertiliser manufacturers to ensure that the declared content effectively corresponds to the quantity solubilised under the conditions of the method.
This document sets out the method of extraction of the following trace elements: total boron, total cobalt, total copper, total iron, total manganese, total molybdenum and total zinc.
The objective is to perform a minimum of extractions so that it can be used, whenever possible, the same extract to determine the total content of each of the aforementioned trace elements.
This method concerns the EEC fertilizers referred to in the Order of 14 June 1991 on fertilizers and related products containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It applies to each of the trace elements whose declared contents are greater than 10 per 100.
23 (e) .2 Material and apparatus.
23 (e) .2.1 Regulable temperature heating plate.
23 (e) .2.2 pHmetro.
Note: If the quantitative determination of boron present in the extract is foreseen, the use of borosilicate glass utensils should be discarded. The use of teflon or silica will be more convenient, as the extraction is boiling. If detergents containing borates are used to wash the glass utensils, they should be carefully clarified.
23 (e) .3 Reassets.
23 (e) .3.1 Diluted hydrochloric acid solution (HCl), approximately 6 M. Mix 1 volume of hydrochloric acid (p = 1.18 g/mg) with 1 volume of water.
23 (e) .3.2 Concentrated ammonia solution (NH OH, p = 0.9 g/ml).
23 (e) .4 Procedure.
23 (e) .4.1 Sample preparation. See method number 1 (Order of 18 July 1989, for which official fertilizer analysis methods are approved)
23 (e) .4.2 Sample collection. Weigh a 1 or 2 g fertilizer amount depending on the declared element content in the product. The following table should be used to obtain a final solution which, once suitably diluted, is in the measurement range of each method. The samples shall be weighed with a precision of 1 mg.
Declared content of the element in the credit (percent). /T 10 R 25/' 25
Sample mass (g). /2/1
Mass of the element in the sample (mg). /T 200 R 500/' 250
Volume of extract V (ml). /500/500
Concentration of the element in the extract (mg/l). /T 400 R 1,000/' 500
Introduce the sample into a 250 milliliter beaker.
23 (e) .4.3 Dissolution. If necessary, moisten the sample with a little water; add dilute hydrochloric acid (23 (e) .3.1) in small fractions and with caution, at the rate of 10 millilitres per gram of fertilizer used; then add approximately 50 ml of water. Plug the beaker with a watch glass and mix. Boil for thirty minutes over the heating plate. Leave to cool, stirring occasionally. Transfer quantitatively to a 500 millilitre graduated flask. Make up with water. Homogenize. Pass through a dry filter to a dry container. Discard the first filter portion. The extract must be perfectly clear.
Proceed as quickly as possible to determinations on aliquot parts of clear filtering. If not, plug the canister.
Observation: The extracts in which the boron content is to be determined shall be carried at a pH of between 4 and 6 with concentrated ammonia (23 (e) .3.2).
23 (e) .4.4 Determination. The determination of each trace element shall be carried out in the aliquot parts indicated in the specific methods of each trace element.
Methods 22 (b), 37 (b), 33 (b), and 35 (b) cannot be used to determine elements present in chelated or complexed form. In such cases, method 23 (g) should be followed before the determination.
This treatment may not be necessary in the determination of atomic absorption spectrophotometry (methods 32 (b) and 29 (b)).
23 (e) .5 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L 86 of 2 April 1995. Method 10.1.
III. METHOD 23 (f)
23 (f) Extraction of water-soluble oligoelements.
23 (f) .1 Principle.
The extraction of the trace elements is carried out by stirring the fertilizer in water at a temperature of 20 ± 2 ° C.
Note: The extraction is empirical and cannot be quantitative.
The method of extracting water-soluble forms from the following trace elements: boron, cobalt, iron, manganese, molybdenum, and zinc is established herein. The objective is to carry out a minimum of extractions so that the same extract can be used whenever possible to determine the content of each of these trace elements.
This method applies to EEC fertilizers referred to in the Order of 14 June 1991 on fertilizers and related products containing one or more of the following trace elements: boron, cobalt, copper, iron, manganese, molybdenum and zinc. It applies to each of the trace elements whose declared contents are greater than 10 per 100.
23 (f) .2 Material and apparatus.
23 (f) .2.1 Rotating Agitator adjusted to 35 or 40 revolutions per minute, approximately.
Note: If the quantitative determination of boron present in the extract is foreseen, the use of borosilicate glass utensils should be discarded. For this extraction the teflon or the silica is preferable. If detergents containing borates are used to wash the glass utensils, they should be carefully clarified.
23 (f) .3 Reassets.
23 (f) .3.1 Diluted hydrochloric acid solution (HCl), approximately 6M. Mix 1 volume of hydrochloric acid (q: 1,18 g/ml) with 1 volume of water.
23 (f) .4 Procedure.
23 (f) .4.1 Sample preparation. See method number 1 (Order of 18 July 1989, for which the official methods of analysis of fertilizers are approved).
23 (f) .4.2 Sample Take. Take a 1 or 2 g fertilizer amount depending on the declared element content in the product. The following table should be used to obtain a final solution which, once suitably diluted, is in the measurement range of each method. The samples shall be weighed with a precision of 1 mg.
Declared content of the element in the credit (percent). /T 10 R 25/' 25
Sample mass (g). /2/1
Mass of the element in the sample (mg). /T 200 R 500/' 250
Volume of extract V (ml). /500/500
Concentration of the element in the extract (mg/l). /T 400 R 1,000/' 500
Place the sample in a 500 ml flask.
23 (f) .4.3 Dissolution. Add approximately 400 ml of water. Cover the flask carefully. Shake vigorously with the hand to obtain a good dispersion of the product. Place the flask in the agitator (23 (f) .2.1). Have the apparatus in operation for thirty minutes. Make up with water. Homogenize. Filter immediately on a clean, dry flask. Plug the flask. Proceed to the determination immediately after filtration.
Note: If a progressive enturbiation of extract is produced, carry out a new extraction according to (23 (f) .4.2) and (23 (f) .4.3) in a volume flask V. Filter on a previously dry volume graduated flask, in which they will be pour 5 ml of dilute hydrochloric acid (23 (f) .3.1). Interrupt the leak at the time the root line is reached. Homogenize.
Under these conditions, the V value shown in the calculations section is:
V = V X W
W-5
The dilutions listed in the calculations section depend on this value of V
23 (f) .4.4 Determination. The determination of each trace element shall be carried out in the aliquot parts indicated in the specific methods of each trace element.
Methods 22 (b), 37 (b), 30 (c), 33 (b) and 35 (b) cannot be used for certain elements present in chelated or complexed form. In such cases, method 23 (g) should be followed before each determination.
This treatment may not be necessary in the determination of atomic absorption spectrophotometry (methods 32 (b) and 29 (b)).
23 (f) .5 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L 86 of 20 April 1995. Method 10.2.
IV. METHOD 23 (g)
23 (g) Elimination of organic compounds in fertilizer extracts in contents greater than 10 per 100.
23 (g) .1 Principle.
The organic compounds contained in the aliquot of the extract are oxidized with hydrogen peroxide.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) for which the Order of 14 June 1991 on fertilizers and related products establishes the quantitative determination of the total element and/or water-soluble element.
The presence of organic matter in small amounts almost never influences the determinations by atomic absorption spectrometry.
23 (g) .2 Material and apparatus.
23 (g) .2.1 Regulable temperature heating plate.
23 (g) .3 Reassets.
23 (g) .3.1 Diluted hydrochloric acid solution, approximately 0.5 M.
Mix 1 volume of hydrochloric acid (HCl, q = 1.18) with 20 volumes of water.
23 (g) .3.2 Hydrogen peroxide solution (HO, q = 1, 1), at 30 per 100 free of trace elements.
23 (g) .4 Procedure.
23 (g) .4.1 Sample preparation. Take 25 ml of the extraction solution according to method 23 (e) or 23 (f) and introduce it into a 100 ml beaker. If the extraction is 23 (f), add 5 ml of the hydrochloric acid solution (23 (g) .3.1).
Add 5 ml of the hydrogen peroxide solution (23 (g) 3.2) below. Cover with a watch glass. Leave to oxidize in cold for about an hour and then boil progressively and keep boiling for half an hour. If necessary, add another 5 ml of hydrogen peroxide to the temperate solution and continue the removal of the organic compounds.
Then remove excess hydrogen peroxide by boiling. Allow to cool and transfer quantitatively to a 50 ml graduated flask. Make up with water. Homogenize. Filter if necessary.
This dilution will be counted at 50 per 100 when taking aliquots and when calculating the percentage of the product trace element.
23 (g) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L 86 of 20 April 1995. Method 10.3.
V. METHOD 23 (h)
23 (h) Quantitative determination of trace elements in contents greater than 10 per 100 in the extracts of fertilizers by atomic absorption spectrometry. (General method.)
23 (h) .1 Principle.
After a possible treatment of the extract, to reduce or eliminate the interfering chemicals, it is diluted in such a way that its concentration is in the optimal response zone of the spectrometer for a wavelength adapted to the element in question.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) for which the Order of 14 June 1991 on fertilizers and related products provides for a declaration of the content of the total and/or water-soluble iron or zinc.
The particular adaptations of this procedure to each trace element are specified in the methods relating to the element in question.
The presence of organic matter in small amounts does not usually influence determinations by atomic absorption spectrometry.
23 (h) .2 Material and apparatus.
23 (h) .2.1 Atomic absorption spectrometer equipped with sources that emit the radiation characteristic lines of the studied elements.
For use, the analyst shall conform to the instructions of the manufacturer of the apparatus and shall be familiar with its use.
The appliance must allow the flame background to be corrected, if necessary (for example, Zn). The gases used will be air and acetylene.
23 (h) .3 Reassets.
23 (h) .3.1 Hydrochloric acid solution approximately 6 M. Mix 1 volume of hydrochloric acid (q = 1,18 g/ml) with 1 volume of water.
23 (h) .3.2 Hydrochloric acid solution approximately 0.5 M. Mix 1 volume of hydrochloric acid (q = 1,18 g/ml) with 20 volumes of water.
23 (h) .3.3 lanthanum salt solutions (10 g per litre). This reagent is used for the quantitative determination of iron and zinc. You can prepare in two ways:
a) With lanthanum oxide dissolved in hydrochloric acid (23 (h) .3.1). In a 1 litre graduated flask, put 11.73 g of lanthanum oxide (LaO) in 150 ml of water and then add 120 ml of 6 M hydrochloric acid (23 (h) .3.1). Let it dissolve and make up with water. Homogenize. The concentration of this hydrochloric acid solution is approximately 0.5 M.
b) With solutions of chloride, sulphate or nitrate of lanthanum. In a 1 litre graduated flask, dissolve 26.7 g of lanthanum chloride heptahydrate (LaCl-7HO) or 31.2 g of lanthanum nitrate hexahydrate (The (NO)-6HO) or 26.2 g of lanthanum sulfate (La (SO)-9HO) in 150 ml of water; add 85 ml of 6M hydrochloric acid (23 (h) .3.1). Let it dissolve and make up with water. The concentration of this hydrochloric acid solution is approximately 0.5 M.
23 (h) .3.4 Pattern solutions. For their preparation see the methods of quantitative determination of each trace element.
23 (h) 4 Procedure.
23 (h) .4.1 Preparation of the problem solution.
23 (h) .4.1.1 Dissolution of the items to be determined. See methods 23 (e) and 23 (f) and, if applicable, 23 (g).
23 (h) .4.1.2 Preparation of the test solution. Dilute an aliquot of the extract obtained by following methods 23 (e), 23 (f) or 23 (g) with water or hydrochloric acid (23 (h) .3.1) or (23 (h) .3.2) so as to obtain, in the final solution for the measure, a concentration of the appropriate element to the range of standard solutions (23 (h) .4.3) and a concentration of hydrochloric acid not less than 0,5 M but not exceeding 2,5 M. This operation may require one or more successive dilutions.
The final solution should be obtained by placing an aliquot of the diluted extract in a 100 ml volumetric flask, the volume being (a) in ml of this aliquot. Add 10 ml of the chosen lanthanum salt solution (23 (h) .3.3). Make up to 0,5 M hydrochloric acid solution (23 (h) .3.2) and homogenise. Be D the dilution factor.
23 (h) .4.2 Preparation of the blank solution. Prepare a blank solution by following the entire process from the extraction and only by omitting the credit sample.
23 (h) .4.3 Preparing the pattern solutions
From the working pattern solution prepared according to the method described for each trace element, prepare, in 100 ml graduated flasks a series of at least five increasing concentration pattern solutions which correspond to the optimal measurement area of the apparatus. If necessary, adjust the concentration of hydrochloric acid to be as close as possible to that of the diluted problem solution (23 (h) .4.1.2). For iron or zinc determination, add 10 ml of the same lanthanum salt solution (23 (h) .3.3) as used in 23 (h) .4.1.2. Make up to 0,5 M hydrochloric acid solution (23 (h) 3.2) and homogenise.
23 (h) .4.4 Measurements. Prepare the spectrometer (23 (h) .2.1) for the determination and regulate the wavelength to the value specified in the method proper to the element to be determined.
Measure three times successively the standard solutions (23 (h) .4.3), the problem solution (23 (h) .4.1.2) and the blank solution (23 (h) .4.2), scoring each result; thoroughly washing the apparatus with distilled water between each measurement.
Represent the pattern curve by placing the mean value of the results of each of the pattern measurements (23 (h) .4.3) read on the spectrometer and, on the abscesses, the corresponding concentrations of the element that is determined, expressed in lg/ml.
From this curve, determine the concentrations of that element in the problem solution X (23 (h) .4.1.2). These concentrations shall be expressed in lg/ml.
23 (h) .5 Calculations.
The percentage of the element (E) in the credit is equal to:
E (%) of Credit = (X-X) X V X D
M X 10
If method 23 (g) has been followed:
E (%) of Credit = (X-X) X V X 2D
M X 10
Being:
E
= the amount of the item that is determined, expressed as a percentage of the credit.
X
= the concentration of the test solution (23 (h) .4.1.2) in lg/ml.
X
= the concentration of the blank solution (23 (h) .4.2) in lg/ml.
V
= the volume of the extract obtained according to method 23 (e) or 23 (f), in ml.
D
= the factor corresponding to the dilution carried out at (23 (h) .4.1.2).
M
= the mass of the sample taken according to Method 23 (e) or 23 (f) in grams.
Calculation of the dilution factor D: if (a), (a), (a), ... (a) and (a) are the aliquots and (v), (v), (v), ... (v) and 100 the volumes corresponding to the respective dilutions, the dilution factor D shall be equal to:
v/v/v/100
D =//X//X ... X//X/
a/a/a
(/) /(/) /(/) /(/)
23 (h) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.4.
VI. METHOD 29 (b)
29 (b) Quantitative determination of zinc in contents greater than 10 per 100 in the extracts of fertilizers by atomic absorption spectrometry.
29 (b) .1 Principle.
Once the extracts are properly treated and diluted, zinc is determined by atomic absorption spectrometry.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) for which the Order of 14 June 1991 on fertilizers and related products provides for the declaration of zinc.
29 (b) .2 Material and appliances
29 (b) .2.1 Atomic absorption spectrometer: see paragraph 23 (h) .2. The apparatus must be provided with a source of radiation characteristic of zinc (213,8 nm) and a background correction.
29 (b) .3 Reassets.
29 (b) .3.1 Hydrochloric acid solution approximately 6 M. See paragraph 23 (h) .3.1.
29 (b) .3.2 Hydrochloric acid solution approximately 0,5 M. See paragraph 23 (h) .3.2.
29 (b) .3.3 lanthanum salt solutions (10 g per litre). See paragraph 23 (h) .3.3.
29 (b) .3.4 Zinc standard solutions.
29 (b) .3.4.1 Zinc solution (1,000 lg/ml). In a 1000 ml graduated flask, dissolve 1 g of zinc powder or plate, weighed with a precision of 0.1 mg in 25 ml of 6 M concentrated hydrochloric acid (29 (b) .3.1). After complete dissolution, make up to scratch with water and homogenize.
29 (b) .3.4.2 Zinc work solution (100 lg/ml). In a 200 ml volumetric flask, dilute 20 ml of the stock solution (29 (b) .3.4.1) with 0,5 M hydrochloric acid solution (29 (b) .3.2). Make up with 0.5 M. Homogenise hydrochloric acid solution.
29 (b) .4 Procedure.
29 (b) .4.1 Preparing the problem solution. Dissolution of zinc. See methods 23 (e) and 23 (f) and, if applicable, 23 (g).
29 (b) .4.2 Preparation of the test solution. See paragraph 23 (h) .4.1.2. The test solution must contain 10 per 100 (v/v) of a lanthanum salt solution.
29 (b) .4.3 Preparation of the blank solution. See paragraph 23 (h) .4.2. The test solution must contain 10 per 100 (v/v) of a lanthanum salt solution used in 29 (b) .4.2.
29 (b) .4.4 Preparation of standard solutions. See paragraph 23 (h) .4.3. For an optimal range of 0 to 5 lg/ml of zinc (Zn), enter, respectively, 0, 0,5, 1, 2, 3, 4 and 5 ml of the working solution 29 (b) .3.4.2 in 100 ml graduated flasks. If necessary, adjust the concentration of hydrochloric acid to be as close as possible to that of the test solution. Add in each flask 10 ml of the lanthanum salt solution used in 29 (b) .4.2. Make up to 0,5 M hydrochloric acid solution (29 (b) .3.2). Homogenize.
These solutions contain, respectively, 0, 0.5, 1, 2, 3, 4 and 5 lg/ml of zinc (Zn).
29 (b) .4.5 Measurements. See paragraph 23 (h) .4.4. Prepare the spectrometer (29 (b) .2.1) to perform the measurements at a wavelength of 213.8 nm.
29 (b) .5 Calculations.
See paragraph 23 (h) .5.
The percentage of zinc (Zn) in the fertilizer is equal to:
Zn (%) = (X-X) X V X D
M X 10
If method 23 (g) has been followed:
Zn (%) = (X-X) X V X 2D
M X 10
Being:
Zn
= the amount of zinc (Zn), expressed as a percentage of the fertilizer.
X
= the concentration of the test solution (29 (b) .4.2) in lg/ml.
X
= the concentration of the blank solution (29 (b) .4.3) in lg/ml.
V
= the volume of the extract obtained according to method 23 (e) or 23 (f), in ml.
D
= the factor corresponding to the dilution carried out in (29 (b) .4.2).
M
= the mass of the sample taken according to Method 23 (e) or 23 (f) in grams.
Calculation of the dilution factor D: if (a), (a), (a), ... (a) and (a) are the aliquots and (v), (v), (v), ... (v) and 100 the volumes corresponding to the respective dilutions, the dilution factor D shall be equal to:
v/v/v/100
D =//X//X ... X//X/
a/a/a
(/) /(/) /(/) /(/)
29 (b) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.11.
VII. METHOD 30 (c)
30 (c) Quantitative determination of copper in fertilizer extracts in contents greater than 10 per 100 by volume.
30 (c) .1 Principle.
A method for the determination of copper in fertilizer extracts is described herein.
The cupric ions are reduced in acid medium with potassium iodide:
2 Cu '' + 4I ' 1 2Cui + I
Iodine thus released is valued with a standard sodium thiosulfate solution in the presence of starch as an indicator, according to the following reaction:
I + 2NaSO 1 2NaI + NaSO
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) or 23 (f) for which the Order of 14 June 1991 on fertilizers and related products provides for the determination of the content of the copper.
30 (c) .2 Reassets.
30 (c) .2.1 nitric acid (HNO, p: 1.40 g/ml)
30 (c) .2.1 Urea ((NH) C = 0)
30 (c) .2.2 Solution to 10 per 100 (w/v) ammonium bifluoride
(NHHF)
Save the solution to a plastic container.
30 (c) .2.3 Ammonium hydroxide solution (1 + 1).
Mix a volume of ammonium hydroxide solution (NHOH, p: 0.9 g/ml) and a volume of water.
30 (c) .2.4 Sodium thiosulfate standard solution. In a 1 litre graduated flask, dissolve 7.812 g of sodium thiosulfate pentahydrate (NaSO, 5HO) in water. This solution must be prepared so that 1 ml is equivalent to 2 mg Cu. Stabilize the solution by adding a few drops of chloroform. The solution should be stored in a glass container and protected from direct light.
30 (c) .2.5 Potassium Yodide (KI)
30 (c) .2.6 Potassium thiocyanate solution (KSCN) at 25 per 100 (w/v). Keep this solution in a plastic bottle.
30 (c) .2.7 Starch solution at approximately 0.5 per 100. Insert in a beaker of 600 ml 2.5 g of starch ((CHO) n). Add approximately 500 ml of water. Bring to the boil agitating. Cool to room temperature. The solution is not preserved long.
30 (c) .3 Procedure.
30 (c) .3.1 Dissolution of copper. See methods 23 (e) and 23 (f).
30 (c) .3.2 Preparation of the test solution. Insert an aliquot of the solution of the extract that does not contain less than 20 or 40 mg of Cu in a 500 ml erlenmeyer. Remove the excess oxygen eventually present by a short boil. Complete the volume up to approximately 100 ml with water. Add 5 ml of nitric acid (30 (c) .2.1) and boil for half a minute.
Remove the erlenmeyer from the heat source, add 3 g, approximately urea (30 (c) .2.1) and boil again for another half minute, approximately.
Remove from the heat source and add 200 ml of cold water. If necessary, cool the contents of the erlenmeyer to room temperature.
Add little to little ammonia (30 (c) .2.3) until the solution turns blue. Then add 1 ml more.
Add 10 g of potassium iodide (30 (c) .2.5) and dissolve.
30 (c) .3.3 Valuation of the solution. Place the erlenmeyer on a magnetic stirrer. Insert the rod into the erlenmeyer and regulate the agitator at the desired speed.
Add with a bureta sodium thiosulfate pattern solution (30 (c) .2.4) until the intensity of the brown iodine released from the solution decreases.
Enter 10 ml of the starch solution (30 (c) .2.7). Continue the assessment with the sodium thiosulfate solution (30 (c) .2.4) until the practice of the purple color.
Add 20 ml of potassium thiocyanate solution (30 (c) .2.6) and continue the assessment until the total disappearance of the violet blue colour.
Annotate the volume used for the thiosulfate solution.
30 (c) .4 Calculations.
1 ml of the sodium thiosulfate standard solution (7.812 mg) corresponds to 2 mg Cu.
The percentage of copper in the fertilizer is:
Cu (%) = X V
to X M X 5
Being:
X
= the volume used in the sodium thiosulfate solution, in ml.
V
= the volume of the extract solution, obtained according to methods 23 (e) or 23 (f), in ml.
a
= the volume of the aliquot part, in ml.
M
= the mass of the sample treated according to methods 23 (e) or 23 (f) in grams.
30 (c) .5 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.7.
VIII. METHOD 32 (b)
32 (b) Quantitative determination of iron in fertilizer extracts in content greater than 10 per 100 by atomic absorption spectrometry.
32 (b) .1 Principle.
A method for iron determination in fertilizer extracts is described herein.
Once the extracts are properly treated and diluted, iron is determined by atomic absorption spectrometry.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) and for which the Order of 14 June 1991 on fertilizers and related products establishes the determination of the Total iron and/or water soluble content.
32 (b) .2 Material and apparatus.
Atomic Absorption Spectrometer, see Method 23 (h). The apparatus must be provided with a source of radiation characteristic of the iron (248.3 nm).
32 (b) .3 Reassets.
32 (b) .3.1 Hydrochloric acid solution, approximately 6 M. See section 3.1 of Method 23 (h).
32 (b) .3.2 Hydrochloric acid solution, approximately 0.5 M. See method 23 (h).
32 (b) .3.3 Hydrogen peroxide solution (HO at 30 per 100, p = 1.11 g/ml) free of trace elements.
32 (b) .3.4 Lanthanum salt solutions (10 g per litre). See paragraph 3.3 of Method 23 (h).
32 (b) .3.5 Iron calibration solutions.
32 (b) .3.5.1 Iron stem solution (1,000 lg/ml). In a 500 ml beaker weigh 1 g of pure iron wire, with a precision of 0.1 mg and add 200 ml of 6M hydrochloric acid (32 (b) .3.1) and 15 ml of peroxide solution (32 (b) .3.3). Heat in heating plate until complete dissolution, allow to cool and pass quantitatively to a flask of 1,000 ml. Make up with water and homogenise. 32 (b) .3.5.2 Iron work solution (100 lg/ml). In a 200 ml graduated flask, enter 20 ml of stock solution (32 (b) .3.5.1). Make up to 0,5 M hydrochloric acid solution (32 (b) .3.2). Homogenize.
32 (b) .4 Procedure.
32 (b) .4.1 Iron dissolution. See methods 23 (e), 23 (f) and if applicable 23 (g).
32 (b) .4.2 Preparation of the test solution. See paragraph 4.1.2 of Method 23 (h). The test solution must contain 10 per 100 (v/v) of a lanthanum salt solution.
32 (b) .4.3 Preparation of the blank solution. See paragraph 4.2 of Method 23 (h). The blank solution must contain 10 per 100 (v/v) of the lanthanum salt solution used in 32 (b) .4.2.
32 (b) .4.4 Preparation of calibration solutions. See paragraph 4.3 of Method 23 (h). For an optimal detection range between zero and 10 lg/ml of iron (Fe), enter respectively in 100 ml graduated flasks: 0, 2, 4, 6, 8 and 10 ml of the working solution (32 (b) .3.5.2). If necessary, adjust the concentration of hydrochloric acid to be as close as possible to that of the test solution. Add 10 ml of the lanthanum salt solution used in 32 (b) .4.2. Make up to 0,5 M hydrochloric acid solution (32 (b) .3.2). Homogenize. These solutions contain, respectively, 0, 2, 4, 6, 8 and 10 lg/ml of iron (Fe).
32 (b) .4.5 Measurements. See section 4.4 of Method 23 (h). Prepare the spectrometer (32 (b) .2) to perform the measurements at a wavelength of 248.3 nm.
32 (b) .5 Calculations.
See method 23 (h).
The percentage of iron (Fe) in the fertilizer is equal to: Fe (%) = ((X-X) X V X 2D)/(M X 10)
Being:
Faith
= amount of iron (Fe), expressed as a percentage of the fertilizer.
X
= the concentration of the test solution (32 (b) .4.2) in lg/ml.
X
= the concentration of the blank solution (32 (b) .4.3) in lg/ml.
V
= the volume of the extract obtained with method 23 (e) or 23 (f) in ml.
D
= the factor corresponding to the dilution carried out in (32 (b) .4.1).
M
= the mass of the sample taken with arrego to Method 23 (e) or 23 (f) in grams.
Calculation of dilution factor D:
If (a), (a), (a) and (a) are the aliquots and (v), (v), (v) ... (v) and (100) the volumes in ml corresponding to the respective dilutions, the dilution factor D shall be equal to:
D = (v/a) X (v/a) X (v/a) x.x.x.x. (v/a) X (100/a)
32 (b) .6 Reference.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.8.
IX. METHOD 33 (b)
33 (b) Quantitative determination of manganese in contents greater than 10 per 100 in the extracts of fertilizer by valuation as permanganate.
33 (b) .1 Principle.
In case there are chloride ions present in the extract, they are removed by boiling the extract, to which sulphuric acid has been added. Manganese is oxidized by sodium bismutate in nitric acid. The permanganate being formed is reduced by an excess of ferrous sulfate. This excess is valued with a potassium permanganate solution.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) for which the Order of 14 June 1991 on fertilizers and related products provides for the declaration of the content of the Manganese
33 (b) .2 Material and apparatus.
33 (b) .2.1 Filter crucible P16/ISO 4793, porosity 4, capacity 50 ml, installed on a 500 ml filtration flask.
33 (b) .2.2 Magnetic Agitator.
33 (b) .3 Reassets.
33 (b) .3.1 Concentrated sulphuric acid (HSO, q: 1.84 g/ml).
33 (b) .3.2 sulphuric acid approximately 9 M. Mix with care 1 volume of concentrated sulphuric acid (33 (b) .3.1) and a volume of water.
33 (b) .3.3 nitric acid 6 M. Mix 3 volumes of nitric acid (HNO, q: 1.40 g/ml) and 4 volumes of water.
33 (b) .3.4 nitric acid 0.3 M. Mix a volume of 6 M nitric acid and 19 volumes of water.
33 (b) .3.5 Sodium Bismutate (NaBiO) to 85 per 100.
33 (b) .3.6 Land of diatoms.
33 (b) .3.7 Orthophosphoric acid 15 M (H4 q: 1.71 g/ml).
33 (b) .3.8 ferrous sulfate solution 0.15 M. In a 1 litre graduated flask, dissolve 41.6 g of ferrous sulphate heptahydrate (FeSO.7HO). Add 25 ml of concentrated sulphuric acid (33 (b) .3.1) and 25 ml of phosphoric acid (33 (b) .3.7). Make up and homogenise.
33 (b) .3.9 Potassium permanganate solution 0.020 M. Pesar, with a precision of 0.1 mg, 3,160 g potassium permanganate (KMnO), dissolve and lead to 1,000 ml of water.
33 (b) .3.10 Silver nitrate solution. Dissolve 1.7 g of silver nitrate (AgNO) and lead to 100 ml with water
33 (b) .4 Procedure.
33 (b) .4.1 Preparing the problem solution.
33 (b) .4.1.1 Dissolution of manganese. See methods 23 (e) and 23 (f).
If there are doubts about the presence of chloride ions, test the solution with a drop of the silver nitrate solution (33 (b) .3.10).
33 (b) .4.1.2 If there is no chloride ion, insert an aliquot of the extract containing 10 to 20 mg of manganese into a glass of 400 ml precipitates. Bring to a volume of approximately 25 ml, either by evaporation or by adding water. Add 2 ml of concentrated sulphuric acid (33 (b) .3.1).
33 (b) .4.1.3 If there are chloride ions, you need to remove them as follows:
In a high precipitous glass of appropriate capacity, enter an aliquot of the extract containing between 10 and 20 mg of manganese. Add 5 ml of 9 M sulphuric acid (33 (b) .3.2). Under an extractor campaign, bring to the boil over the heating plate and keep boiling until there is an abundant release of white fumes. Continue until the volume is reduced to approximately 2 ml (thin layer of liquid at the bottom of the glass). Bring the beaker back to room temperature again. Add 25 ml of water carefully and check once again the absence of chlorides with a drop of the silver nitrate solution (33 (b) .3.10). If chlorides remain, start the operation again after having added 5 ml of 9 M sulphuric acid (33 (b) .3.2).
33 (b) .4.2 In a 400 ml beaker containing the problem solution, put 25 ml of 6 M nitric acid (33 (b) .3.3) and 2.5 g of sodium bismutate (33 (b) .3.5). With the magnetic stirrer (33 (b) .2.2), shake vigorously for three minutes. Add 50 ml of 0.3 M nitric acid (33 (b) .3.4) and shake again.
Filter vacuum with a crucible (33 (b) .2.1) whose bottom has been covered in diatoms (33 (b) .3.6). Wash the crucible several times with nitric acid 0.3 M (33 (b) .3.4) until a colourless filter is obtained.
Transfer the filtering and washing solution to a 500 ml beaker. Mix and add 25 ml of the 0,15 M ferrous sulphate solution (33 (b) .3.8). If the filtrate becomes yellow after the addition of ferrous sulphate, add 3 ml of 15 M orthophosphoric acid (33 (b) .3.7).
Value by a burette the excess ferrous sulfate with the potassium permanganate solution 0.02 M (33 (b) .3.9) until a stable pink color is obtained for one minute.
Make a blank determination under the same conditions by omitting only the sample.
Note: The oxidized solution should not come into contact with rubber.
33 (b) .5 Calculations.
1 ml of potassium permanganate solution 0.02 M corresponds to 1.099 mg manganese (Mn).
Mn (%) of Credit = (X-X) X 0.1099 X V
to X M
Being:
X
= the volume of the permanganate used in the blank test, in ml.
X
= the volume of the permanganate used in the test with the sample, in ml.
V
= the volume of the extract obtained according to methods 23 (e) and 23 (f), in ml.
a
= the volume of the aliquot taken from the extract, in ml.
M
= the mass of the sample, in grams.
33 (b) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.9.
X. METHOD 35 (b)
35 (b) Quantitative determination of molybdenum in contents greater than 10 per 100 in the extracts of fertilizers by gravimetry with 8-hydroxyquinoline.
35 (b) .1 Principle.
The quantitative determination of molybdenum is performed by precipitation as molybdenyl oxinate under certain conditions.
This method applies to extracts from the samples of fertilizers obtained by methods 23 (e) and 23 (f) for which the Order of 14 June 1991 on fertilizers and related products provides for the declaration of Molybdenum.
35 (b) .2 Material and apparatus.
35 (b) .2.1 Filter crucible P16/ISO 4793, porosity 4, capacity 30 ml.
35 (b) .2.2 pHmeter with glass electrodes.
35 (b) .2.3 Regulated drying at 130-135 ° C.
35 (b) .3 Reassets.
35 (b) .3.1 sulphuric acid solution, approximately 1 M. In a 1 litre graduated flask containing 800 ml of water, care for 55 ml of sulphuric acid (HSO, q = 1.84 g/ml). Homogenize. Leave to cool and complete up to 1 litre. Homogenize.
35 (b) .3.2 Diluted ammoniacal solution (1: 3). Mix 1 volume of concentrated ammonia (NHOH, q = 0.9 g/ml) and 3 volumes of water.
35 (b) .3.3 Diluted acetic acid solution (1: 3). Mix 1 volume of concentrated acetic acid (99.7 per 100 CHCOOH, q = 1,049 g/ml) and 3 volumes of water.
35 (b) .3.4 Solution of disodium salt of ethylenediaminetetraacetic acid (EDTA). In a 100 ml graduated flask, dissolve in water 5 g NaEDTA. Make up and homogenise.
35 (b) .3.5 Buffer solution. In a 100 ml graduated flask, dissolve 15 ml of concentrated acetic acid and 30 g of ammonium acetate in water. Make up.
35 (b) .3.6 Solution of 8-hydroxyquinoline (oxin). In a 100 ml graduated flask, dissolve 3 g of hydroxyquinoline in 5 ml of concentrated acetic acid. Add 80 ml of water. Add drop-by-drop solution ammoniacal (35 (b) .3.2) until the solution is muddled, and then acetic acid (35 (b) .3.3) until the solution is clear again. Make up with water.
35 (b) .4 Procedure.
35 (b) .4.1 Preparing the problem solution. Dissolution of molybdenum. See methods 23 (e) and 23 (f).
35 (b) .4.2 Preparation of the test solution. Insert in a glass of 250 ml precipitates an aliquot containing between 25 and 100 mg of Mo. Complete the volume with water up to 50 ml.
Bring this solution to a pH of 5 by adding drop to drop of the sulphuric acid solution (35 (b) .3.1).
Add 15 ml of EDTA solution (35 (b) .3.4) and then 5 ml buffer solution (35 (b) .3.5). Complete up to approximately 80 ml with water.
35 (b) .4.3 Obtaining and washing the precipitate. Getting the precipitate. Heat the solution slightly. While stirring constantly, add the oxin solution (35 (b) .3.6). Continue precipitation until sediment formation is no longer observed. Add excess reagent until the supernatant solution takes a slight yellow colour. Normally, a quantity of 20 ml should be sufficient. Continue to heat the precipitate slightly for 2 or 3 minutes.
Filtration and washing. Filter with a filter crucible (35 (b) .2.1). Rinse several times with volumes of 20 ml of hot water. Rinse water should be made progressively colourless, indicating that there is no longer any oxin.
35 (b) .4.4 Heavy of precipitate. Dry the precipitate at 130-135 ° C until constant weight (one hour at least). Allow to cool in a desiccator and weigh.
35 (b) .5 Calculations.
1 mg of molybdenyl oxinate, MoO (CHON) corresponds to 0.2305 mg of Mo
Mo (%) of the fertilizer = X X 0,02305 X V X D
to X M
Being:
X
= the mass of the molybdenyl oxinate precipitate, in
mg.
V
= the volume of the solution of the extract obtained according to method 23 (e) or 23 (f), in ml.
a
= the volume of the aliquot taken from the last dilution, in ml.
D
= the dilution factor of this aliquot.
M
= the mass of the sample, in grams.
35 (b) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.10.
XI. METHOD 37 (b)
37 (b) Quantitative determination of cobalt in fertilizer extracts, of contents greater than 10 per 100, by gravimetry with 1-nitroso-2-naphthol.
37 (b) .1 Principle.
A method for the determination of cobalt in fertilizer extracts is described herein.
The procedure described applies to extracts of fertilizers obtained by methods 23 (e) or 23 (f), for which the Order of 14 June 1991 on fertilizers and related products provides for the declaration of the content of the cobalt.
cobalt III forms with 1-nitroso-2-naphthol a red precipitate of Co (CHONO) .2HO.
After carrying the cobalt present in the extract to the state of cobalt III, the cobalt is precipitated in acetic medium by a solution of 1-nitroso-2-naphthol. After filtering, the precipitate is washed and dried to constant weight and subsequently weighed as Co (CHONO) .2HO.
37 (b) .2 Material and apparatus.
37 (b) .2.1 Filter crucible P 16 /ISO 4793, porosity 4, capacity 30 or 50 ml.
37 (b) .2.2 Regulated desiccation to 130 ± 2 ° C.
37 (b) .3 Reassets.
37 (b) .3.1 Hydrogen peroxide solution at 30 per 100 (HO, q = 1.11 g/ml).
37 (b) .3.2 Sodium hydroxide solution, approximately 2 M.
Dissolve 8 g of sodium hydroxide in lentils in 100 ml of water.
37 (b) .3.3 Diluted hydrochloric acid solution, approximately 6 M. Mix 1 volume of hydrochloric acid (q = 1,18 g/ml) and 1 volume of water.
37 (b) .3.4 acetic acid (99.7 per 100 CHCOH, q = 1.05 g/ml).
37 (b) .3.5 acetic acid solution 1: 2 (approximately 6 M). Mix a volume of acetic acid (37 (b) .3.4) and 2 volumes of water.
37 (b) .3.6 Solution of 1-nitroso-2-naphthol in acetic acid. Dissolve 4 g of 1-nitroso-2-naphthol in 100 ml acetic acid (37 (b) .3.4). Add 100 ml of warm water. Homogenize. Filter immediately. The solution obtained must be used at the moment.
37 (b) .4 Procedure.
37 (b) .4.1 Dissolution of cobalt. See methods 23 (e) and 23 (f).
37 (b) .4.2 Preparation of the test solution. Insert an aliquot of the extract containing no more than 20 mg of Co into a 400 ml beaker.
If the extract has been obtained according to method 23 (f), acidify with five drops of hydrochloric acid (37 (b) .3.3).
Add about 10 ml of hydrogen peroxide solution (37 (b) .3.1).
Let the oxidant act in cold for fifteen minutes and then add water up to about 100 ml. Plug the beaker with a watch glass.
Heat and keep boiling for about ten minutes. Cool. Alkalinize by adding drop to drop solution of sodium hydroxide (37 (b) .3.2) until the black cobalt hydroxide begins to precipitate.
Add 10 ml of acetic acid (37 (b) .3.4) and complete with water up to approximately 200 ml. Heat until it starts to boil. Add 20 ml of the 1-nitroso-2-naphthol solution (37 (b) .3.6) with bureta with bureta 20 ml. End with energetic agitation so that the precipitate is coagulated.
Filter on a pre-tarted filter crucible (37 (b) .2.1), avoiding the colkilling of the crucible. To do this, check that there is liquid above the precipitate throughout the entire leak.
Wash the beaker with diluted acetic acid (37 (b) .3.5) to drag the entire precipitate, wash the precipitate over the filter with diluted acetic acid (37 (b) .3.5) and then three times with hot water.
Dry a stove (37 (b) .2.2) at 130 ± 2 ° C until it reaches a constant weight.
37 (b) .5 Calculations.
1 mg of Co precipitate (CHONO) .2HO corresponds to 0,096381 mg of Co.
The percentage of cobalt (Co) in the fertilizer is:
Co (%) = X X 0.0096381 X V X D
to X M
Being:
X
= the mass of the precipitate, in mg.
V
= the volume of the solution of the extract obtained according to method 23 (e) or 23 (f), in ml.
a
= the volume of the aliquot taken from the last dilution, in ml.
D
= the dilution factor of this aliquot.
M
= the mass of the sample, in grams.
37 (b) .6 References.
Commission Directive 95 /8/EC. 'Official Journal of the European Communities' number L86 of 20 April 1995. Method 10.6.
