on the Borates of Barium. 61 



with 150^° of hot water and analyzed for carbon dioxide. The 

 result was as follows: 



Bai;OH), taken, 0-4379 grm.; Bfi, taken, 0-1788 grm. ; alco- 

 hol, 76 per cent ; CO^ found, 0-1135 grm. ; CO, in total barium 

 carbonate, 0-1121 grm. 



Upon evaporating to small volume the filtrate from this 

 experiment, boric acid in abundance crystallized from the solu- 

 tion. Under these conditions, then, well within the limits of 

 the recommendations of the Morse and Burton process, it is 

 clear that barium metaborate is completely converted into 

 carbonate with consequent liberation of boric acid, and that 

 alcoholic solutions in no way prevent the action. 



It might be argued that, in an evaporating mixture contain- 

 ing barium carbonate and boric acid in 78 per cent solution, 

 the reaction would be reversed after the volatilization of the 

 alcohol and the solutions became more concentrated. Indeed, 

 Morse and Horn use this explanation (p. 110). To test this 

 hypothesis, equivalent parts of barium hydrate and boric acid 

 in alcohol were treated with carbon dioxide for two hours, the 

 mixture evaporated to dryness and the carbon dioxide remain- 

 ing in the dry residue determined. The following results 

 were obtained : 



Ba(OH), taken, 0-1551 grm. : ^fi, taken, 0-1860 grm. ; 

 alcohol, 82 percent; CO, found, 0-1018 grm.; CO^ in total 

 barium carbonate, 0-1169 grm. This shows that even with the 

 very strong alcoholic solution, which was used by mistake, 

 about 90 per cent of the metaborate was converted into carbo- 

 nate and remained as carbonate after bringing to dryness. 



To demonstrate, in another way, the presence of boric acid 

 after the treatment recommended by Morse and Burton, I 

 have used the methyl alcohol flame-test. Equivalents of 

 barium hydrate and boric acid (I have used the word equiva- 

 lents repeatedly, meaning quantities to form exactly the most 

 important salt under discussion, viz : metaborate) were evapo- 

 rated to dryness, methyl alcohol added and burned without 

 getting the slightest indication of free boric acid. Again, 

 equivalents of iDarium hydrate and boric acid were treated 

 in alcoholic solution with carbon dioxide, the ethyl alcohol 

 and water removed by evaporation, and methyl alcohol applied 

 and burned with unmistakable indications of free boric acid — 

 burning with a solid green flame. 



Since free boric acid does not decompose barium carbonate 

 upon evaporation, the question arises as to what is the tem- 

 perature required to bring about this decomposition. The 

 following experiment throws some light upon this point : finely 

 divided anhydrous boric acid (0-li925 grm.) and barium car- 

 bonate (0-5177 grm.) were mixed in a platinum crucible, 



