GB/T 2592.7-1981 Determination of lead in thallium (chrome blue cyanine S absorptiometry) GB/T2592.7-1981 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China Determination of Aluminum in Thallium (Chromium Blue Cyanine S Absorptiometry) General Principles and General Provisions GB1467-78 shall be followed. 1. Method Summary GB2592.7-81 In the medium of hexamethylenetetramine at pH 5-6, aluminum and chrome blue cyanine S form a purple-red complex dissolved in water, and its absorbance is measured at a wavelength of 560nm. The presence of 20 micrograms of zinc, cadmium, silver, mercury, bismuth and thallium in the test solution has no effect on the determination. Under the masking of sodium sulfite and thiourea, the presence of 30 micrograms of copper, iron, lead, indium, 50 micrograms of tellurium, cadmium, zinc, silver, 40 micrograms of mercury, bismuth and 25 milligrams of thallium has no effect on the determination. Thallium has no effect on the determination after being separated by thallium chloride precipitation in 10% hydrochloric acid medium. Determination range: 0.0005~0.0030%.
2. Reagents
Hydrochloric acid (specific gravity 1.19), (1+1), (0.5N). Nitric acid (1+1).
Ammonium hydroxide (1+1). www.bzxz.net
Thiourea saturated solution.
Sodium sulfite solution (2%): Prepare it when used. Hexamethylenetetramine solution (20%).
Bromocresol green indicator (0.05%): Weigh 0.05 g of bromocresol green, dissolve it in 50 ml of anhydrous ethanol, dilute it to 100 ml with water, and shake it.
Chrome blue cyanine S solution (0.05%): Weigh 0.1 g of chrome blue cyanine S, dissolve it in 50 ml of anhydrous ethanol, dilute it with water to 200 ml, and shake it.
Aluminum standard solution:
(A) Weigh 0.5000 g of metallic aluminum (99.95%), place it in a 250 ml beaker, add 20 ml of hydrochloric acid (1+1), heat to dissolve, add a small amount of water, heat to boil, cool, transfer to a 1000 ml volumetric flask, dilute to the mark with water, and shake well. This solution contains 500 micrograms of aluminum in 1 ml.
(B) Transfer 5.00 ml of solution (A), place it in a 500 ml volumetric flask, add 2 ml of hydrochloric acid (1+1), dilute to the mark with water, and shake it. This solution contains 5 micrograms of aluminum in 1 ml. 3. Analysis steps
Weigh 1.0000 g of sample (together with the sample as a reagent blank), place in a 100 ml beaker, add 2 ml of nitric acid, dissolve at low temperature, blow the surface III and the wall of the cup with 8 ml of water, add 1 ml of hydrochloric acid (specific gravity 1.19) dropwise to precipitate the thallium chloride completely, cool, filter with absorbent cotton into a 100 ml beaker 1., wash the beaker and funnel with 0.5N hydrochloric acid 3 times each. Heat the filtrate to evaporate to dryness, add 5 drops of hydrochloric acid (1+1)2, add a small amount of water, heat to dissolve the salts, and cool. Transfer to a 50 ml colorimetric tube, dilute with water to 20 ml, add 2 ml of sodium sulfite solution, shake well, and let stand for 2 minutes. Add 1 drop of bromocresol green indicator, neutralize with ammonium hydroxide until the indicator just turns blue, then adjust with 0.5N hydrochloric acid until it just turns yellow and add 3.0 ml excess, shake well. Add 2 ml of saturated thiourea solution and shake well. Add 2.50 ml of chrome blue S solution and shake well. Add 5 ml of hexamethylenetetramine solution, dilute to the mark with water, and shake well. After leaving for 5 to 10 minutes, transfer it to a 1-mm liquid tank, use water as a reference, and measure its absorbance at a wavelength of 560nm on a spectrophotometer. Subtract the absorbance of the reagent blank and calculate the corresponding aluminum amount from the working curve. Drawing of working curve:
Pipette 0.00, 1.00, 2.00, 3.00, 4.00, 5.00 ml of aluminum standard solution (B), place them in a set of 50 ml colorimetric tubes, add 5 drops of hydrochloric acid (1+1), add water to 20 ml, and operate according to the following analysis steps to measure its absorbance. Subtract the absorbance of the standard solution without aluminum and draw the working curve.
The percentage of aluminum is calculated as follows:
Al(%) =W+×10 6
Where: w, the amount of aluminum (micrograms) found from the working curve: W-the sample weight (grams).
4. Allowable difference
0.(005-0.0010
0.0010~0,0020
-0.H)20-0.0030
（“，）
Note: Because the filter paper contains a relatively high amount of boron, the boron will be dissolved during filtration and enter the test solution. The gap is too high and unstable, so the filter paper cannot be used. 2 The presence of a large amount of ammonium salt will reduce the absorbance. Experiments have proved that after adding 5 drops of hydrochloric acid "1+1" to dissolve the residue, carefully neutralize it with ammonium ammonia until the indicator just turns blue, and its absorbance is stable at 42
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