3'22 



On Chemical Tests. 



[Oct. 



a. Lime water soon spoils if exposed to the air. It is made by ad- 

 ding distilled water to fresh slacked lime and stirring it repeatedly du- 

 ring 24 hours. It should be kept in well stoppered bottles. 



b. Where neither uncombined carbonic acid, alkaline nor earthy- 

 carbonates, alumina, nor oxide of iron exist in a mineral water, lime 

 water is one of the best precipitants of magnesia. One twelfth part of 

 a grain in a pint of water may be detected. 



c. Lime water decomposes a neutral solution of platina if exposed 

 to the sun's rays. See 96, d. 



76. lithia, the detection of this substance by re-agents is some- 

 what difficult. But the lithia in salts of lithia may be detected before 

 the blow-pipe. When a portion is melted upon the end of a platina 

 wire bent into a ring, and the melted mass is placed at the point of the 

 inner flame, then the outer flame acquires a beautiful and very strong 

 carmine red colour, see 115 g. The chloride of lithium acts the most 

 strikingly. When the lithia salt is mixed with a potash salt, then the red 

 colour alone is produced before the blow-pipe, and the presence of po- 

 tash, even when the assay contains more potash than lithia, cannot be 

 detected by its behaviour before the blow-pipe. When on the contrary, 

 a lithia salt is mixed with a salt of soda, then only the re-action of the 

 soda is observable, and the outer flame, even when an excess of lithia 

 is present, acquires merely a yellow colour. This is also the case when 

 a lithia salt contains salts of both potash and soda. 



a. The spirituous solutions of lithia salts burn with a beautiful 

 carmine red flame, particularly when the spirit is nearly consumed, and * 

 the burning liquid is stirred with a glass rod. 



b. The presence of lithia, in solutions of the salts of lithia, is best 

 determined as follows. The operator first assures himself, by the ad- 

 dition of a solution of carbonate of potash or carbonate of soda, that the 

 salt in solution is actually an alkaline salt, which point is determined if 

 this test, on being added to a not very concentrated solution of the 

 compound, produces no precipitate. In the next place, if the solution 

 be not troubled by solutions of tartaric acid and chloride of platinum, 

 the absence of potash is determined. If farther, the solution, on being 

 mixed with a solution of phosphate of soda and ammonia, produces, 

 after some time, a strong precipitate, the presence of lithia is deter- 

 mined, and that substance is hereby distinguished, more particularly 

 from soda, but also from potash. Finally, lithia can be sufficiently 

 discriminated from the other two alkalies by its behaviour before the 

 blow-pipe. 



