1.

Method 2 is amended as follows: (a) Method 2.1 is amended as follows: (i) points 4.2 to 4.7 are replaced by the following: ‘4.2. Sulphuric acid: 0,05 mol/l for variant a. 4.3. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.4. Sulphuric acid: 0,1 mol/l for variant b (see note 2). 4.5. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.6. Sulphuric acid: 0,25 mol/l for variant c (see note 2).’ 4.7. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (ii) in point 9, table 1, variant a, the second sentence is replaced by the following: ‘Sulphuric acid 0,05 mol/l to be placed in the receiving flask: 50 ml’; (iii) in point 9, table 1, variant b, the second sentence is replaced by the following: ‘Sulphuric acid 0,1 mol/l to be placed in the receiving flask: 50 ml’; (iv) in point 9, table 1, variant c, the second sentence is replaced by the following: ‘Sulphuric acid 0,25 mol/l to be placed in the receiving flask: 35 ml’; (b) in Method 2.2.1, point 4.2 is replaced by the following: ‘4.2. Sulphuric acid 0,05 mol/l’; (c) Method 2.2.2 is amended as follows: (i) points 4.2 to 4.7 are replaced by the following: ‘4.2. Sulphuric acid: 0,05 mol/l for variant a. 4.3. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.4. Sulphuric acid: 0,1 mol/l for variant b (see note 2, Method 2.1). 4.5. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.6. Sulphuric acid: 0,25 mol/l for variant c (see note 2, Method 2.1).’ 4.7. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (ii) point 7.4 is replaced by the following: ‘7.4. Control test Before analysing, check that the apparatus is working properly and that the correct technique is applied using an aliquot part of a freshly prepared solution of sodium nitrate (4.13) containing 0,050 to 0,150 g of nitrate nitrogen depending on the variant chosen.’; (d) in Method 2.2.3, points 4.2 to 4.7 are replaced by the following: ‘4.2. Sulphuric acid: 0,05 mol/l for variant a. 4.3. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.4. Sulphuric acid: 0,1 mol/l for variant b (see note 2, Method 2.1). 4.5. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.6. Sulphuric acid: 0,25 mol/l for variant c (see note 2, Method 2.1).’ 4.7. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (e) in Method 2.3.1, points 4.5 to 4.10 are replaced by the following: ‘4.5. Sulphuric acid: 0,05 mol/l for variant a (see Method 2.1). 4.6. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.7. Sulphuric acid: 0,1 mol/l for variant b (see note 2, Method 2.1). 4.8. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.9. Sulphuric acid: 0,25 mol/l for variant c (see note 2, Method 2.1).’ 4.10. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (f) in Method 2.3.2, points 4.4 to 4.9 are replaced by the following: ‘4.4. Sulphuric acid: 0,05 mol/l for variant a (see Method 2.1). 4.5. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.6. Sulphuric acid: 0,1 mol/l for variant b (see note 2, Method 2.1). 4.7. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.8. Sulphuric acid: 0,25 mol/l for variant c (see note 2, Method 2.1).’ 4.9. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (g) in Method 2.3.3, points 4.3 to 4.8 are replaced by the following: ‘4.3. Sulphuric acid: 0,05 mol/l for variant a (see Method 2.1). 4.4. Sodium or potassium hydroxide solution, carbonate free: 0,1 mol/l 4.5. Sulphuric acid: 0,1 mol/l for variant b (see note 2, Method 2.1). 4.6. Sodium or potassium hydroxide solution, carbonate free: 0,2 mol/l 4.7. Sulphuric acid: 0,25 mol/l for variant c (see note 2, Method 2.1).’ 4.8. Sodium or potassium hydroxide solution, carbonate free: 0,5 mol/l (h) in Method 2.4, point 4.8 is replaced by the following: ‘4.8. Sulphuric acid: 0,05 mol/l’; (i) Method 2.5 is amended as follows: (i) point 4.2 is replaced by the following: ‘4.2. Sulphuric acid solution, about 0,05 mol/l’; (ii) in point 7.1, the second sentence is replaced by the following: ‘Make up the volumes to about 50 ml with water, add one drop of indicator (4.7) and neutralise, if necessary, with sulphuric acid 0,05 mol/l (4.2).’; (iii) point 7.3, the first paragraph is replaced by the following: ‘According to the presumed biuret content, transfer 25 or 50 ml from the solution mentioned in 7.2 with a pipette, place this quantity in a 100 ml graduated flask and neutralise if necessary with a 0,05 mol/l or a 0,1 mol/l reagent (4.2 or 4.3) as required, using methyl red as an indicator and add, with the same accuracy as that used when drawing up a calibration curve, 20 ml of the alkaline solution of potassium sodium tartrate (4.4) and 20 ml of the copper solution (4.5). Make up to volume, mix thoroughly and leave standing for 15 minutes at 30 (± 2) °C.’; (j) Method 2.6.1 is amended as follows: (i) point 4.8 is replaced by the following: ‘4.8. Standard solution of sulphuric acid: 0,1 mol/l’; (ii) point 4.17 is replaced by the following: ‘4.17. Standard sulphuric acid solution: 0,05 mol/l’; (iii) in point 7.1.1.2, the first sentence of the first paragraph is replaced by the following: ‘Transfer with a precision pipette, into the receiver of the apparatus, 50 ml of a standard solution of sulphuric acid 0,1 mol/l (4.8).’; (iv) in point 7.1.1.4, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,2 mol/l, used for the blank, carried out by pipetting into the receiver of the apparatus (5.1), 50 ml of standard solution of sulphuric acid 0,1 mol/l (4.8),’; (v) in point 7.1.2.6, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,2 mol/l, used for the blank, carried out by pipetting into the receiver of the apparatus (5.1), 50 ml of standard solution of sulphuric acid 0,1 mol/l (4.8),’; (vi) in point 7.2.2.4, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,2 mol/l, used for the blank, carried out by pipetting into the receiver of the apparatus (5.1), 50 ml of standard solution of sulphuric acid 0,1 mol/l (4.8),’; (vii) in point 7.2.3.2, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,2 mol/l, used for the blank, carried out by pipetting into the receiver of the apparatus (5.1), 50 ml of standard solution of sulphuric acid 0,1 mol/l (4.8),’; (viii) in point 7.2.5.2, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,2 mol/l, used for the blank, carried out by pipetting into the receiver of the apparatus (5.1), 50 ml of standard solution of sulphuric acid 0,1 mol/l (4.8),’; (ix) in point 7.2.5.3, the first three sentences are replaced by the following: ‘Transfer with a precision pipette, into the dry flask of the apparatus (5.2), an aliquot sample of the filtrate (7.2.1.1 or 7.2.1.2) containing 20 mg of ammoniacal nitrogen at the most. Then assemble the apparatus. Pipette, into the 300 ml Erlenmeyer, 50 ml of the standard sulphuric acid solution 0,05 mol/l (4.17) and enough distilled water for the level of the liquid to be approximately 5 cm above the opening of the delivery tube.’; (x) in point 7.2.5.5, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of standard solution of sodium or potassium hydroxide 0,1 mol/l, used for the blank, carried out by pipetting into the 300 ml Erlenmeyer of the apparatus (5.2), 50 ml of standard solution of sulphuric acid 0,05 mol/l (4.17),’; (k) Method 2.6.2 is amended as follows: (i) point 4.6 is replaced by the following: ‘4.6. Sulphuric acid solution 0,1 mol/l’; (ii) point 4.14 is replaced by the following: ‘4.14. Titrated sulphuric acid solution: 0,05 mol/l’; (iii) in point 7.2.4, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of titrated 0,2 mol/l sodium or potassium hydroxide solution (4.8), used in the blank test, carried out by placing 50 ml of titrated 0,1 mol/l sulphuric acid solution into the receiver of the apparatus (4.6),’; (iv) in point 7.3.3, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of titrated 0,2 mol/l sodium or potassium hydroxide solution (4.8), used in the blank test, carried out by pipetting 50 ml of titrated 0,1 mol/l sulphuric acid solution (4.6) into the receiver of the apparatus,’; (v) in point 7.5.1, the third sentence of the first paragraph is replaced by the following: ‘Pipette into the 300 ml Erlenmeyer exactly 50 ml of titrated 0,05 mol/l sulphuric acid solution (4.14) and an amount of distilled water so that the level of the liquid is approximately 5 cm above the opening of the intake tube.’; (vi) in point 7.5.3, the explanation of the element ‘a’ of the formula is replaced by the following: ‘a= ml of titrated 0,1 mol/l sodium or potassium hydroxide solution (4.17), used in the blank test, carried out by pipetting into the 300 ml Erlenmeyer of the apparatus (5.2) 50 ml of titrated 0,05 mol/l sulphuric acid solution (4.14).’.