GB/T 24268-2009Test methods for chemical analysis of silver-tin oxide electric contact material (English PDF)

2.1 Principle of the method

After the decomposition of nitric acid with ammonium sulfate as an indicator, with potassium thiocyanate standard titration solution titration, thiocyanate first with the solution

Silver ion reaction to produce insoluble silver thiocyanate silver precipitate, when the silver ions precipitate completely, excess of a drop of thiocyanate and ferric ions

Generating red iron thiocyanate complex, that is, the end point.

2.2 Reagents

2.2.1 nitric acid

Nitric acid (1 + 1).

2.2.2 Potassium thiocyanate standard titration solution

Potassium thiocyanate standard titration solution [c (KCNS) = 0.04 mol/L].

2.2.2.1 preparation

Weigh about 9.7g potassium thiocyanate dissolved in water, diluted to 2500mL, fully mixed evenly, put it aside for 3 days.

2.2.2.2 Calibration

Weigh 0.1000 g of sterilized silver (99.99%) in 250 mL Erlenmeyer flask, add 10 mL of nitric acid (2.2.1), heat at low temperature

Dissolved, boiled to remove the yellow smoke, cooled to room temperature, add water to 100mL, add 5mL ammonium ferric sulfate (2.2.3), with potassium thiocyanate standard titration solution

Liquid (2.2.2) titrated to light red as the end point.

Per kilogram of potassium thiocyanate standard titration solution is equivalent to the amount of silver according to formula (1).

(1)

Where.

V - titration of pure silver consumed by potassium thiocyanate standard titration solution in milliliters (mL).

Weigh 2g of ammonium ferric sulfate dissolved in 100mL water, dropping just boiled nitric acid (2.2.1) to brown faded.

2.3 Analysis steps

2.3.1 Determine the environment

Determination of the environment should be no hydrochloric acid mist.

2.3.2 sample

Weigh 0.1g sample, accurate to 0.0001g.

2.3.3 Determination

2.3.3.1

Place the sample (2.3.2) in a 250 mL Erlenmeyer flask and add 10 mL of nitric acid (2.2.1) to the furnace for low temperature heating.

The material is completely dissolved and boiled to remove the yellow smoke and cool to room temperature.