摄影 摄影级化学品 试验方法 第3部分:不溶于氢氧化铵溶液物质的测定

[中文适用范围]： GB/T 20432的本部分规定了照相级化学品氨水不溶物（氨水与钙、镁形成的沉淀物）测定的通用试验方法。 [外文原描述]： The method is based on weighing a test portion, dissolution in water, addition of ammonium oxalate solution, diammonium hydrogen phosphate solution and ammonium hydroxide solution, allowing to stand for at least 8 h, filtering out the precipitate through filter paper, transfer of the filter paper with precipitate to a prepared crucible, burning it over a gas burner, incineration of the residue in a furnace, cooling in a desiccator, and reweighing.