374 Confribuiions to Experimental Chemistry, 



precipitate. By evaporating, or by decomposing a more con- 

 centrated solution of the chloride, very small dark red crystals 

 are obtained. 



In the proto-nitrate of mercury the silicate of soda produces 

 a white precipitate, which only becomes decomposed if heated 

 with caustic alkali. 



In the sulphate of manganese a white precipitate is formed. 



A solution of nitrate of silver becomes yellowish without pre- 

 cipitation, whilst a solution of the same concentration was 

 copiously precipitated by caustic soda. Nitrate of cobalt and 

 protochloride of tin were not precipitated by the silicate, whilst 

 caustic soda produced precipitates in solutions of the same 

 degree of dilution. Perchloride of tin, chloride of zinc, and 

 nitrate of copper are more copiously precipitated by the silicate 

 of soda, than by the hydrate. 



Silicate of potash bears an analogous relation to the per- 

 chloride of iron. 



On the Separation of Lime from Magnesia, 



The oxalates of ammonia and potash have of late been re- 

 sorted to almost exclusively for this purpose, on account of 

 their precipitating very diluted solutions of lime. Professor 

 PfafF states, that in a solution, containing -jooocy of chloride of 

 lime, a precipitate is formed after a few minutes, and that the 

 reaction is at its limit (after a few hours) when to oVtt^ of sul- 

 phate or muriate of lime are present in solution. Analysts 

 have advised not to precipitate from a too concentrated or 

 from a warm solution^ and to avoid an excess of ammonia, in 

 order to prevent the precipitation of the magnesia. I know 

 not whether there have been any direct experiments to prove 

 what influence magnesian salts have in modifying the delicacy 

 of \he oxalates as a test for lime : I have, therefore, endea- 

 voured to examine this point by the following experiments : 



Sulphate of lime and chloride of calcium dissolved with 

 different proportions of sulphate of magnesia, or anhydrous 

 muriate of magnesia, in water sufficient to raise the weight of 

 the whole liquid to 2000 times that of the calcareous salts, 

 gave the following results when precipitated by oxalate of am- 

 monia or oxalate of potash. 



