Reagent and solution

1, sulfuric acid solution (1+8): absorb 20mL sulfuric acid, slowly add 160mL water, stirring constantly.

2 (100g/L), potassium iodide solution: weigh 20 g of potassium iodide, into 200mL water, with new.

3, starch indicator solution (5g/L): weigh 0.5g starch, 100mL dissolved in boiling water, with new.

4, the standard sodium thiosulfate solution [C (Na2S2O3) =0.100mol/L]: 26G sodium thiosulfate and 0.2g sodium carbonate are weighed, add appropriate amount of freshly boiled water to dissolve, and dilution to 1000ml, mixing, turn brown reagent bottle, placed a month after filtration, the accurate calibration standby.

A sodium thiosulfate standard solution of the calibration precision weighing about 0.15g in 120 drying to constant weight, potassium dichromate (national standard reference material GBW 06105c), placed in 500ml flask iodine, add 50 ml of water to dissolve. Join 2G Ki, shake gently to dissolve, then add 20mL sulfuric acid solution (1), closed, shake. Put in the dark after 10min with 250mL water dilution. Dripping with sodium thiosulfate standard titration solution to solution is light yellow, then add 3ml starch indicator solution (3), continue the titration to the disappearance of the blue and light green. The temperature of the reaction liquid and the dilution water should not be higher than 20. At the same time to do a good reagent blank test.

The concentration of standard solution of B sodium concentration was calculated by formula (1).

m

C (Na2S2O3.5H2O) =..................... (1).

(V-V blank) x 0.04903

Formula: C (Na2S2O3.5H2O): the actual concentration of sodium sodium sulfate standard solution, mol/L;

M: the quality of potassium dichromate, g;

V: the dosage of sodium sodium sulfate standard solution, mL;

V blank: the amount of sodium in the standard solution of reagent blank test, mL;

0.04903: with 1 mL standard solution of sodium thiosulfate (C (Na2S2O3.5H2O) =1.000 mol/L) is potassium dichromate, G.

Determination of sodium chlorite weighing steps about 3G, accurate to 0.0002g and placed in a 100 ml beaker, dissolve it in water, all moved into a 500 ml volumetric flask, dilute with water to scale, shake.

Volume 10 ml of solution, placed in the pretreatment with 20 ml of potassium iodide solution (2) 250ml flask iodine, and add 20 ml of sulphuric acid solution (1) and shake it up. In the dark place 10min. Add 100ml water, sodium thiosulfate standard solution (4) titration solution to a pale yellow, add about 3ml starch indicator solution (3), continue the titration to the disappearance of the blue as an end, meanwhile, the blank test is made.

Presentation and calculation of results

Sodium perchlorate (NaClO2) content (X1) content () calculated by mass fraction (2):

(V1-V 1) x C1 x 0.02261

X1= x 100

M x 10/500

113.05 (V1-V 1) C1

=....................................... (2).

M type: the percentage of the mass of X1:NaClO2,%;

V1: the volume of the standard solution of sodium sodium sulfate standard solution, mL;

V blank 1: the volume of the standard solution of sodium salt consumed by the blank test, mL;

C1: the concentration of sodium sodium sulfate standard solution, mol/L;

0.0226:1.00mL sodium sulfate solution c (Na2S2O3) mol/L =1.000 is equivalent to the quality of sodium hypochlorite, g;

M: sodium perchlorate, G.

The difference between the 0.2% parallel test results is no more than two, and the average value of the results is determined by the results.