GB/T 223.25-1994Methods for chemical analysis of iron, steel and alloy--The dimethylglyoxime gravimetric method forthe determination of nickel content (English PDF)

3.1

Hydrochloric acid (rho1.19 g/mL).

3.2

Hydrochloric acid (1+1).

3.3

Nitric acid (rho1.42 g/mL).

3.4

Perchloric acid (rho1.67 g/mL).

3.5

Aqua ammonia (rho0.90 g/mL).

3.6

Aqua ammonia (1+1).

3.7

Tartaric acid solution (50%).

3.8 Anhydrous sodium sulfite solution (20%)

Prepare when used, and use after filtration.

4.2.3

USE slow-speed filter paper to filter; PLACE the filtrate in a 600 mL beaker;

USE hot water to wash the beaker; WASH the filter paper and precipitate 7~8 times. The total volume of the solution is controlled to about 250 mL.

4.2.4

Under constant stirring, use hydrochloric acid (3.2) to acidify the solution to about pH 3.5; ADD 20 mL of anhydrous sodium sulfite solution (3.8) and stir for a while; USE aqua ammonia (3.6) to adjust the solution to pH 4.5. When heated to 45~50°C, add sodium thiosulfate solution (3.9) (when the copper content is less than 30 mg, add 10 mL; when it exceeds 30 mg, add 20 mL);

STIR for a while and place 5 min.

4.2.5

ADD dimethylglyoxime ethanol solution (3.11) (calculated according to adding 0.6 mL per 1 mg of nickel, cobalt and copper, and with an excess of 10 mL). Under constant stirring, add 20 mL of ammonium acetate solution (3.10).

At this time, the pH of the solution shall be 6.0~6.4. If it is lower than this range, it can be adjusted with aqua ammonia (3.6).

4.2.6

Adjust the total volume of the solution to about 400 mL (the samples containing cobalt or copper can be controlled at about 500 mL); LET it stand and age for 30 min (the samples containing cobalt and copper are aged for 1 h).

4.2.7

COOL down to room temperature; USE a constant weight of No. 4 glass crucible for vacuum filtration (the speed should not be too fast; the precipitate must not be sucked dry). USE cold water to wash the beaker and the precipitate (to prevent the precipitate from being sucked dry. It is better to wash with a small amount of water in many times and make the precipitate disperse. The total amount of washing water is generally controlled at about 200 mL).

4.2.8

PUT the glass crucible in an oven; DRY it at 145±5°C for about 2 h; COOL it in a desiccator; WEIGH it, and dry it repeatedly to a constant weight.