Preliminary tests for and separation of certain anions

18 PRELIMINARY TESTS FOR AND SEPARATION OF CERTAIN ANIONS After the systematic separation and detection of cations, the search for anions should be started. At this stage already considerable information is available about the presence or absence of certain anions. Not only the preliminary wet and dry tests supplied this information, but during the separation of cations a number of facts became available thus the presence of phosphate, borate, fluoride, citrate, tartrate, and oxalate has been detected, before the precipitation of Group III cations. Similarly, the presence of chromate (or dichromate), permanganate and arsenate has been established at various stages of these separations. When the systematic examination for anions is carried out, such findings should be kept in mind. 

Before describing these preliminary tests, a summary of the solubilities of the salts of the more common anions in water may be found useful in the subsequent deductions. 

Nitrates, chlorates, acetates, manganates, and permanganates are all soluble exceptions are a few basic nitrates (e.g. Bi and Sb) and basic acetates (e.g. Fe) silver and mercury(I) acetates are sparingly soluble. 

Nitrites are all soluble silver nitrite is sparingly soluble. 

Chlorides are generally soluble exceptions are AgCl, Hg2Cl2, T1C1, CuCl, SbOCl, BiOCl, which are insoluble PbCl2 is sparingly soluble. 

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