1839.] 



On Chemical Tests. 



299 



^drive off, also, any excess of the ammoniacal carbonate, which might 

 have retained in solution, either yttria, glucina, or zirconia. The alka« 

 line salts may be separated from these earths, by boiling the mixture in 

 water, and filtering and evaporating it. The salts, with bases of fixed 

 alkalies, will remain unvolatilized. By this process, indeed, it will be 

 impossible to ascertain whether ammoniacal salts were originally pre- 

 sent; but this may be easily learned, by adding to the salt under exa- 

 mination, before its solution in water, potash; which, if ammonia be 

 contained in the salt, will produce the peculiar smell of that alkali. 



33. AMMONIA, hydro- sulphur et of. This test acts on a great num- 

 ber of the metals. See the tables of re-agents. 



34. AMMONIA, hydro-chlorate, or muriate of, or sal- ammoniac, de- 

 tects platinum, producing a bright yellow precipitate, if the platinum 

 be pure. If a solution contain both gold and platinum, the gold may 

 be precipitated by green sulphate of iron, see 67, and the platinum by 

 muriate of ammonia. This test separates alumina from its alkaline so- 

 lutions ; the alkali combines with the muriatic acid, and the liberated 

 ammonia determines the precipitation of the alumina, which after being 

 washed and dried, is perfectly pure. 



a. Muriate of ammonia dissolves more or less of all the earthy car- 

 bonates when both are together in solution, See pages 95, 178 and 333, 

 of the London and Edinburgh Journal of Science, A. D. 1837, for its 

 action on metals. 



b. Sulphate of lead is completely decomposed by a solution of muri- 

 ate of ammonia ; which also acts upon silver with the assistance of air 

 and dissolves it. Muriate of silver is partially dissolved by a concen- 

 trated solution of muriate of ammonia, and is still further acted on if 

 boiled. 



c. Sal-ammoniac or muriate of ammonia used as a test, ought to be 

 entirely volatilized by a low heat, when laid on a heated iron; if sub 

 phate of ammonia be also present in it, it may be detected by baryta, 

 see 40. 



35 ammonia, oxalate of is a capital test for detecting lime which 

 it is said to indicate, if lime be diluted to the extent of 24,000 times its 

 weight in water. It also occasions a cloudiness with magnesia, but the 

 mngnesia does not precipitate till it has stood for several hours. In using 

 this test or oxalic acid, if a mineral acid be present, it must be neutra- 



