Determination of Sn ^{2 +}

(1) Reagents
1 N iodine solution;
1% starch indicator
20% sulfuric acid.
② Analysis
Take 20 ml of plating solution, add 20 ml of 20% sulfuric acid, add 50 ml of water, titrate with 0.1N iodine solution, and titrate with starch as indicator until the blue color does not disappear.
③ Calculation of tin content in bath
Sn2+=NV1*0.059*1000/V（g/L）
In the formula:
N-equivalent concentration of standard iodine solution;
V1-consumption of iodine solution in titration (ML);
V-sample volume (ML).

Measurement of lead ion

(1) Reagents
20% sulfuric acid
② Analysis
Take 5ml of plating solution, add 100ml of water, add 20ml of 20% sulfuric acid, heat and boil for 2-3min, cool to room temperature, filter the precipitate and wash with methanol, then dry the sample in 100 ℃ oven for one hour, cool to room temperature and weigh.
③ Calculation of lead content in plating bath:
Sn2+=[G*0.6833/V]*1000（g/L）
In the formula:
G-mass of precipitate (g)
V-sample volume (ML)

Determination of free fluoroboric acid

(1) Reagents
1 mol/L NaOH aqueous solution
② Analysis
Take 10 ml of plating solution and put it in a 100 ml conical flask. Titrate it with 1 mol/L sodium hydroxide until it is turbid.
③ Calculation of lead content in plating bath:
[HBF4]=[CV1*0.0879/V]*1000(g/L)
In the formula:
N-equivalent concentration of standard NaOH solution;
Consumption of v-naoh solution (ML)
V -- sample volume (ML)

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