GB/T 5195.4-1985 Chemical analysis method of fluorspar - Iodometric method for determination of sulfide content GB/T5195.4-1985 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis methods of fluorspar
Iodometric method for the determination of sulphide content
This standard is applicable to the determination of sulfide content in fluorspar. Determination range: ≥0.001%. UDC 549.454
：543:661
GB5195.4—85
ISO 4284—1978
This standard is equivalent to the international standard ISO4284—1978 "Acid grade fluorspar-Determination of sulfide content-Iodometric method". This standard is not applicable to the determination of sulfide content in fluorspar containing polysulfides. This standard complies with GB1467-78 "General principles and general provisions of chemical analysis method standards for metallurgical products". 1 Method Summary
Place the sample in a closed distillation apparatus, add a mixture of hydrochloric acid, stannous chloride and boric acid, heat and decompose the sample, release hydrogen sulfide, which is carried out by a stream of oxygen-free nitrogen or argon and absorbed by a cadmium acetate solution, and the generated sulfide is determined by iodine titration. ? Reagents
2.1 Boric acid.
2.2 Oxygen-free nitrogen (or argon).
If the nitrogen contains oxygen, first let the nitrogen pass through a wash bottle containing pyrogallic acid solution. Preparation of alkaline pyrogallic acid: Mix 50ml of 25% pyrogallic acid solution and 50ml of 30% potassium hydroxide solution. 2.3 Hydrochloric acid (1+2).
2.4 Tin chloride solution (20%): Weigh 20g of stannous chloride (SnCl22HzO), place it in 30ml of hydrochloric acid (specific gravity 1.19), dilute it with water to 100ml, and mix well.
2.5 Potassium iodide solution (20%).
2.6 Acetic acid solution (3%): Weigh 30g of cadmium acetate [Cd(CH,CO0)2°2H,0], place it in an appropriate amount of water containing 6ml of glacial acetic acid, and dilute it with water to 1000ml. 2.7 Starch solution (0.5%).
2.8 Iodine standard solution (0.01N).
Dilute it with 0.1N iodine standard solution before use. Preparation of 0.1N iodine standard solution: weigh 6.3g iodine and 10g potassium iodide, put them in a mortar and add a small amount of water to grind until all the iodine is dissolved, transfer them to a 500ml volumetric flask, dilute them with water to the mark, mix them well, and store them in a brown bottle. 2.9 Potassium dichromate standard solution (0.1000N): weigh 4.9035g potassium dichromate (reference reagent) that has been dried at 150-170℃ for 1h and placed in a desiccator to cool to room temperature, dissolve it in water, transfer it to a 1000ml volumetric flask, dilute it with water to the mark, and mix it well. 2.10 Sodium thiosulfate standard solution (0.01N): dilute it with 0.1N sodium thiosulfate standard solution before use. Preparation of 0.1N sodium thiosulfate standard solution: weigh 12.5g sodium thiosulfate, dissolve it in water, add 0.1g sodium carbonate, transfer it to a 500ml volumetric flask, dilute it with water to the mark, and mix it well. Store in brown bottles. 2.10.1 Calibration of sodium thiosulfate standard solution: Pipette 20.00 ml of potassium dichromate standard solution in three portions and place in three 300 ml conical bottles. Add 8 ml of hydrochloric acid (2.3) and 10 ml of potassium iodide (2.5). Mix well. Cover with a small gauge. Quickly place in a dark place for 5 to 10 minutes. Add H to 100 ml of water. Titrate with sodium thiosulfate solution until light yellow. Add 2 ml of starch solution (2.7). Continue titrating until the solution turns bright green (the last drop needs to be shaken vigorously to avoid overdosage). Calculate the equivalent concentration of sodium thiosulfate according to formula (1): N
Wherein: N is the equivalent concentration of sodium thiosulfate; N2-
is the equivalent concentration of potassium dichromate standard solution; N2V2
V2-the volume of potassium dichromate standard solution transferred, ml;-the volume of sodium thiosulfate consumed in titration, ml. 3 Instruments
3.1 The sulfur measuring device is shown in the figure.
1-absorption bottle; 2-dropping funnel, 3-reflux water condenser, 4-flat bottom beaker 3.2 Electric oven that can be controlled at 105±1℃. 4 Samples
4.1 The sample should pass through a 240-day sieve.
4.2 The sample needs to be dried at 105±1℃ for 2h in advance, taken out, placed in a desiccator, and cooled to room temperature. 5 Analysis steps
5.1 Determination quantity
During analysis, a sample should be weighed for determination and the average value should be taken. 5.2 Sample quantity
Weigh 3.0000g sample.
5.3 Blank test
Carry out a blank test with the sample.
5.4 Determination
GB5195.4--85
5.4.1 Transfer 50m2 of cadmium acetate (2.6) and place it in an absorption bottle (4.1.1). Place the weighed sample (6.2) in a flask (4.1.4), add 3g of boric acid (2.1), install the instrument (4.1), place 50ml of hydrochloric acid (2.3) and 10ml of tin nitrate solution (2.4) in a dropping funnel, and then put them in the flask (4.1.4). Pass nitrogen or argon into the device (with a glass tube plugged into the neck of the dropping funnel) at a flow rate of 50 ml/min for 15 min. 5.4.2 Heat the flask and keep it at a slight boil for 1 h without interrupting the gas flow, then remove the absorption bottle from the device. 5.4.3 Remove the gas tube from the absorption bottle, add 10 ml of iodine standard solution (2.8) and 8-10 ml of hydrochloric acid (2.3), and fill the gas tube into the absorption bottle. Pay attention to completely dissolve the cadmium sulfide adhering to the gas tube, then rinse carefully with water and collect the washing liquid in the same bottle.wwW.bzxz.Net
5.4.4 Back-titrate the iodine in the absorption bottle with sodium thiosulfate standard solution (2.9). 6 Calculation of analysis results
Calculate the percentage of sulfide (in terms of sulfur) according to formula (2): s(%)
Vo--
(10.0 - V) -(10.0 - Vo)
-x 0.016 ×
X 100 × 0.00016 x
-The volume of sodium thiosulfate standard solution consumed in the titration with the sample blank, mlV,-The volume of sodium thiosulfate standard solution consumed in the titration of the sample, ml10.0-The volume of iodine standard solution added to the absorption bottle, ml, 0.00016-
-1ml0.01N sodium thiosulfate solution equivalent to sulfur, g; the equivalent concentration of sodium thiosulfate calibrated before use; N-
7Allowance difference
The equivalent concentration of sodium thiosulfate specified when using 0.00016; Sample amount, g.
The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. Sulfide (in terms of sulfur)
0.001~0.005
≥0.005~0.010
20.010 ~0.050
Additional remarks:
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Zhejiang Chongshi Mining Company. This standard was drafted by Zhejiang Metallurgical Research Institute. The main drafters of the standard are Jiang Shaoxu, Wang Yong and Tao Lan. 1.6
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