Intelligence and Miscellaneous Articles. 259 



The best and most certain method of separating boracic acid from 

 bases, is that well known, of converting, by means of hydrofluoric 

 and sulphuric acids, the boracic acid into fluoride of boron, in order 

 to obtain the bases in the state of sulphates. By treating the bo- 

 racic salt with sulphuric acid and alcohol, the boracic acid may like- 

 wise be completely sejDarated in the form of boracic Esther. 



This method is much inferior to that in which hydrofluoric acid is 

 employed to effect the decomposition, and ought not to be employed, 

 except when, for want of a platina retort, concentrated hydrofluoric 

 acid is not obtainable. If, instead of sulphuric acid, hydrochloric 

 acid be employed, as proposed long since by G. G. Gmelin, the 

 boracic aether is not produced with so much facility as by sulphuric 

 acid ; the boracic acid is slowly and imperfectly volatilized. 



As boracic acid does not form with any base a compound which is 

 completely insoluble in water, no method for the direct estimation 

 of boracic acid is at present known. The only combination by 

 means of which boracic acid is completely separable is the fluo- 

 boruret of potassium ; this is not soluble in alcohol. Berzelius states 

 that it is slightly soluble, but it amounts to nothing. It is more 

 soluble in a solution of chloride of ammonium than in pure water. 



A great number of experiments have shown that it is impossible 

 to estimate boracic acid in the state of fluoboruret of potassium. It 

 often happens that it is contained in solution in the state of pure 

 boracic acid uncombined with any base. If hydrofluoric acid be 

 added to the solution, and then carbonate of lime to eliminate the 

 excess of acid added, and lastly, acetic acid and alcohol to the filtered 

 solution, fluoboruret of potassium is obtained, which always contains 

 fluoboruret of calcium. But if the boracic acid is combined with a 

 base, soda for example, and the operation be conducted as described, 

 the results appear to be still more uncertain. 



As to what relates to the separation of boracic and phosphoric 

 acids, M. de Kobell has proposed to operate by adding to the solu- 

 tion of these two acids a solution of chloride of iron, and to precipi- 

 tate the whole by an excess of carbonate of lime. 



The addition of a solution of chloride of iron is not necessary. If 

 to a solution of a compound of boracic acid hydrochloric acid be 

 added, and the mixture be treated cold with excess of carbonate of 

 barytes, the insoluble portion contains no boracic acid, and consists 

 entirely of carbonate of barytes. On the other hand, phosphoric 

 acid, whether free or combined with bases, is completely precipitated 

 cold by carbonate of barytes when a little hydrochloric acid is added 

 to the solution. 



The separation of boracic and phosphoric acids may then be eflfected 

 by carbonate of barytes ; but tlie greatest degree of accuracy is not 

 thus attained, because phosphate of barytes is not absolutely inso- 

 luble in a concentrated solution of borax ; some time after the solu- 

 tion has been filtered, traces both of barytes and ])hosphoric acid are 

 obtained ; the latter is readily discovered by molybdate of ammonia. 



If a mixture of salts of boracic and phosphoric acids, after the ad- 

 S 2 



