(a) Salts of the alkaline earths are precipitated by alkali hydroxides and 

 carbonates, phosphates, borates, oxalates (the corresponding insoluble 

 salts of the alkaline earths being formed). The free acids which would 

 form corresponding salts are also incompatible. 



(&) Salts of the metals in solution are incompatible with hydrates, car- 

 bonates, phosphates, oxalates and the corresponding acids; in many cases 

 with proteins, tannins, acacia and often alkaloids and phenozone. Silver, 

 mercurous, lead, and bismuth salts also with bromides and iodides: the same 

 metals and calcium, barium and strontium, with sulphates and sulphuric 

 acid. 



(c) Hydrates or carbonates of the alkalies, sodium, potassium, and am- 

 monia with salts of metals and alkaline earths, and with alkaloids and some 

 glucosides. 



(d) Alkaloids form insoluble salts with other organic acids than acetic 

 and citric; the free alkaloid being very much less soluble than the salts is 

 precipitated by alkali hydrates and carbonates and by borax. Ammonium 

 carbonate and the bicarbonates do not so readily cause precipitation. 

 Iodides, bromides, salicylates, benzoates, usually cause a precipitate tannic 

 acid, and iodine in a solution of mercuric iodide; precipitation may be pre- 

 vented in many of these cases by from 15-50% of alcohol. About 15% 

 suffices to prevent that by bicarbonates and carbonates. Alkaloides 

 may give a precipitate with many metallic salts especially those of mercury. 



(e) Proteins are precipitated by alkaloids, many metal salts, tannin and 

 alcohol. 



3. Resulting in a change of colour owing to the formation of some 

 soluble but undesired body owing to the interaction of two other sub- 

 stances in solution. 



(a) Giving an objectional appearance tannic and gallic acids and iron 

 preparations, ammonia and carbolic acid; gallic acid and thymol. Ferric 

 chloride with salicylates, carbolic acid, creasote, guaiacol, salol, acetanilid, 

 phenazone, phenacetin, oils of wintergreen, cloves, pimenta, and thyme, 

 podophyllin, aloin, gamboge, asafetida, storax, myrrh, balsam of Peru, 

 balsam of Tolu, morphine and apomorphine. 



(&) The change in colour is the indication of a chemical change ob- 

 jectionable from the pharmacological side also. Salicylates, phenozone, 

 acetanilid, with the free nitrous acid in Spirits of Nitrous Ether (isomtrosc 

 compounds are formed). 



4. Resulting in the chemical splitting of one of the bodies and the for- 

 mation of an undesired body. 



(a) Resulting in the freeing of a volatile body, which may in part or 

 entirely dependent upon the amount formed, remain in solution, 

 drochloric acid with nitric acid (nitrous oxides freed); strong acids 

 alcohol (ethers); acids and carbonates; acids and sulphides; m 



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