IO MICRO-CHEMICAL REAGENTS. 



The commercial potassic hydrate is used in an 

 aqueous or alcoholic solution, whose concentra- 

 tion depends upon the particular purpose for which 

 it is to be employed. In general, a moderately 

 concentrated solution is preferable, since it may 

 be diluted when this is necessary, and a very 

 strong solution is seldom to be recommended, 

 since, although its action is more rapid, it destroys 

 the tissues too quickly. In making an aqueous 

 solution, care should be taken to add the alkali in 

 small quantities, to avoid undue heating. The 

 alcoholic solution is made as follows : r 85-90 per 

 cent, alcohol is mixed with a concentrated aqueous 

 solution of caustic potash until a precipitate is 

 formed. After being repeatedly shaken it is set 

 aside for twenty-four hours, at the end of which 

 time the clear, pale-yellow fluid is decanted, and, 

 after dilution with distilled water, is ready for use. 

 Russow recommends the employment of solutions 

 of two densities, one consisting of one part of dis- 

 tilled water and two parts of the saturated solu- 

 tion ; the other, of one part of water to three of 

 the original solution. 



Since potash solutions readily take up carbonic 

 acid from the air, and further tend to crystallize 

 out in the neck of the bottle in which they are 

 kept, it is necessary to keep them in bottles with 

 glass stoppers, which must be frequently loosened. 



l Russow: Mem. Acad. St. Petersbourg, Ser. 7, Tome 19, No. i, p. 15, 

 note. 



