1、BRITISH STANDARD BS 2690-102: 1979 Methods of testing Water used in industry Part 102: Hydrazine: spectrophotometric method (4-dimethylaminobenzaldehyde) IMPORTANT NOTE. It is essential that this Part be read in conjunction with the information in Part100 of this standard, “Foreword, scope and gener
2、al requirements”, which is published separately. UDC 628.1:663.63.01:543.3:546.171.5BS2690-102:1979 This British Standard, having been prepared under the direction of the Environment and Pollution Standards Committee, was published under the authority of the Executive Board on 31 January 1979 BSI 08
3、-1999 The following BSI references relate to the work on this standard: Committee reference EPC/37 Draft for comment 77/50234 DC ISBN 0 580 10613 6 A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct
4、application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i and ii, pages 1 and 2 and a back cover. This standard has been updated (see copyright date) and may have h
5、ad amendments incorporated. This will be indicated in the amendment table on the inside front cover. Amendments issued since publication Amd. No. Date of issue CommentsBS2690-102:1979 BSI 08-1999 i Contents Page 1 Scope 1 2 Range 1 3 Maximum size of test portion 1 4 Principle 1 5 Interferences 1 6 R
6、eagents 1 7 Sampling 1 8 Preparation of calibration graph 1 9 Procedure 1 10 Calculation 2ii blankBS2690-102:1979 BSI 08-1999 1 1 Scope The method described is for the determination of hydrazine in industrial waters. 2 Range 0.5 4g to 5 4g hydrazine. 3 Maximum size of test portion The maximum size o
7、f test portion is 20 ml. 4 Principle Hydrazine reacts with 4-dimethylaminobenzaldehyde to give acid salts of the azine that are intensely red in strong solutions and yellow in dilute solutions. 5 Interferences Under the conditions described in the method the presence of 100 4g of ammonia, cyclohexyl
8、amine, morpholine, octadecylamine, iron, copper and nickel and 5000 4g of chloride, sulphate and phosphate either separately or collectively do not cause significant interference. 6 Reagents The following reagents are required. 6.1 4-dimethylaminobenzaldehyde solution. Dissolve 4.0 g of 4-dimethylam
9、inobenzaldehyde (grade for hydrazine determination) in 200 ml of methanol and 20 ml of concentrated hydrochloric acid, 36 % (m/m) (11N). Store in a dark bottle out of direct sunlight. 6.2 Hydrochloric acid solution, 0.5N. 6.3 Hydrochloric acid/methanol solution. Mix 20 ml of concentrated hydrochlori
10、c acid, 36 % (m/m) (11N), with 200 ml of methanol. 6.4 Hydrazine standard solutions 6.4.1 Hydrazine stock solution. Dissolve 0.082 g of hydrazine dihydrochloride in 0.5N hydrochloric acid and dilute with this acid to 1 litre. 6.4.2 Hydrazine working solution. Dilute 1 ml of hydrazine solution with 0
11、.5N hydrochloric acid to100 ml. 1 ml N 0.25 g N4 g N 2 H 4 . 7 Sampling If the temperature of the sample is above 25 C it is necessary to use an efficient stainless steel cooling coil so that the temperature of the sample is reduced to about 15 C to 25 C. Insert the outlet tube from the cooling coil
12、 into a 250 ml stoppered bottle so that it almost reaches the bottom. Allow the water to flow until a representative sample is obtained. Withdraw the outlet slowly and immediately stopper the bottle avoiding trapping any air bubbles in the bottle. The sample should then be analysed without delay. 8
13、Preparation of calibration graph Measure accurately volumes of the hydrazine working solution containing 0, 1, 2, 3, 4 and 5 4g of N 2 H 4into a series of previously dried 50 ml one-mark volumetric flasks, each containing 15 ml of 0.5N hydrochloric acid. Then add enough water to each flask to make t
14、he total volume approximately38 ml. Stopper and mix. Adjust the temperature of the contents of each flask to between20 C and 25 C, add 10 ml of 4-dimethylaminobenzaldehyde solution to each, make-up to the mark with water, stopper and mix. Allow to stand for 10 min. Measure the absorbance of each sol
15、ution using 40 mm cells at a known temperature between 20 C and 25 C in a spectrophotometer at the wavelength corresponding to maximum absorption (approximately 458 nm but the exact wavelength shall be checked for each spectrophotometer). Use water in the compensating cell. Deduct the reading for th
16、e blank solution containing no added hydrazine from those obtained for the standard solutions. Plot a graph of the net absorbance against corresponding micrograms of hydrazine. 9 Procedure Measure a suitable volume of the sample (not greater than 20 ml) into a 50 ml one-mark volumetric flask contain
17、ing 15 ml of the 0.5N hydrochloric acid. Add enough water to make the total volume approximately 38 ml. Stopper and mix. Adjust the temperature to within 1 C of the calibration temperature, add 10 ml of the 4-dimethylaminobenzaldehyde solution and make up to the mark with water. Stopper and mix. Mea
18、sure 20 ml of water into a second 50 ml one-mark volumetric flask containing 15 ml of the0.5N hydrochloric acid to serve as a blank. Stopper and mix. Adjust the temperature to within1 C of the calibration temperature, add10ml of the 4-dimethylaminobenzaldehyde solution, make up to the mark with wate
19、r. Stopper and mix. Allow to stand for 10 min.BS2690-102:1979 2 BSI 08-1999 Measure the absorbance of the sample solution and the blank solution using 40 mm cells in the spectrophotometer at a temperature within 1 C of that at which the calibration graph was prepared and at the same wavelength. Use
20、water in the compensating cell. If it is necessary to compensate for the colour of the sample, take a volume equal to that of the test portion and proceed as before but substituting 10 ml of the hydrochloric acid/methanol solution for the4-dimethylaminobenzaldehyde solution and making up to a volume
21、 of 50 ml with water. Measure the absorbance of this compensating solution against water. 10 Calculation Deduct the reading obtained for the blank solution and the colour compensating solution, if used, from that obtained for the sample solution and read off from the calibration graph the hydrazine
22、content of. the test portion. Hydrazine (as N 2 H 4 ), mg/l of test sample = where m is the mass of hydrazine in the test portion(4g) v is the volume of the test portion (ml). m v -3 blankBS 2690-102: 1979 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent
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