GB/T 7686-2016General method for determination of arsenic content of chemical products (English PDF)

3.1 Principles

In the hydrochloric acid medium, arsenic is reduced with zinc to form arsine, and silver diethyldithiocarbamate [Ag (DDTC)] pyridine or trichloride

Methane solution, the formation of purple soluble silver colloidal silver, at the maximum absorption wavelength of 540nm, the absorbance of its measurement.

The reaction formula for the formation of colloidal silver is.

AsH3 6Ag (DDTC) = 6Ag 3H (DDTC) As (DDTC) 3

3.2 General provisions

The reagents and water used in the present method, when not otherwise specified, refer to the analytical reagent and the three reagents that meet the requirements of GB/T 6682

Water level. All reagents, especially zinc particles, should not contain arsenic or only a very small amount of arsenic.

3.3 Reagents and materials

3.3.1

Hydrochloric acid.

3.3.2 zinc particles

particle size of 0.5mm ~ 1mm. If other forms of zinc, should be experimentally proven, under the specified test conditions (see attached)

Recorded A) can give the same result.

3.3.3

Absorbent Solution A. Diethyldithiocarbamate solution [abbreviated as Ag (DDTC) pyridine solution], 5g/L.

Dissolve 1 g of silver diethyldithiocarbamate in pyridine (density about 0.980 g/mL) and dilute to.200 mL with pyridine and store

Sealed brown glass bottle, to avoid light exposure, valid for two weeks.

For the purification of silver diethyldithiocarbamate, see Appendix B.

3.3.4 Absorbent liquid B

Diethyldithiocarbamate trichloromethane solution [abbreviated as Ag (DDTC) trichloromethane solution], 2.5 g/L.

Weigh 0.25 g of silver diethyldithiocarbamate, and then rinsed with an appropriate amount of chloroform. Add 1.0 mL of triethanolamine, and then use […]