OP ARTS AND SCIENCES. 



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the distillate ; but- that, if the mixtures were permitted to stand some 

 hours before distilling, the oxide passed to the semi-gelatiuous con- 

 dition of the hydrate, and retained the boric acid so firmly that tur- 

 meric failed to show the presence of the latter in the distillate. It is 

 plain, therefore, that with sufficient preliminary exposure magnesia 

 might be relied upon to retain boric acid ; but inasmuch as long and 

 perhaps somewhat indefinite periods of waiting are objectionable in 

 any analytical process, it was thought best to try the effect of substi- 

 tuting lime for magnesia. Experiments (9) to (12), conducted like 

 the previous ones, excepting only the use of carefully prepared and 

 ignited calcium oxide instead of magnesium oxide, were made with 

 this end in view. 



These figures indicate sufficiently that there is no loss of boric acid 

 by volatilization when its aqueous solution is evaporated in contact 

 with calcium hydrate ; but, inasmuch as the comparative solubility of 

 the latter is the quality which makes it effective where magnesia is not, 

 it seemed desirable to test the action of calcium hydrate in alcoholic 

 solutions, in which it is very insoluble. The experiment showed that 

 when the solution of boric acid in methyl or ethyl alcohol is put upon 

 lime and distilled at once loss is apt to take place, and sometimes to a 

 very inconsiderable amount, but that a short period of digestion with 

 occasional stirring — from five to fifteen minutes — is sufficient to 

 obviate danger of volatilization of boric acid. 



It appears, therefore, that, free boric acid being easily volatilized by 

 means of methyl alcohol and fixed completely by calcic hydrate, the 

 separation of the acid from almost everything with which it occurs or- 

 dinarily and its estimation subsequently depend only upon the practi- 

 cability of distilling it from its compounds in such company that it may 

 be retained by lime and its amount determined by the increase in the 

 weight of the latter. Unlike magnesium chloride, calcium chloride 

 does not yield its chlorine readily under the action of heat and 

 moisture naturally retained ; so that hydrochloric acid must not be 

 present with boric acid which is to be estimated in the manner de- 

 scribed. Calcium nitrate and calcium acetate both yield the oxide 



