50 Jones — Action of Carhon Dioxide 



a platinum dish^ evaporated to dryness, and heated to a con- 

 stant iceight over a trip)le hurnerr'^ 



In my original article I made three claims: 1st, that the 

 metaborate of barium may be decomposed by gaseons carbon 

 dioxide ; 2d, that the boric acid thus '' liberated " may be lost 

 by volatilization ; 3d, that the metaborate of barium and the 

 carbonate may interact at high temperatures with the loss of 

 carbon dioxide. These facts preclude the use of the method 

 described by Morse and Burton for the determination of boric 

 acid. The more recent experiments of Morse and Horn not 

 only substantiate these facts but disclose a fourth objection to 

 the use of this method for its original purpose, viz : the diffi- 

 cult dehydration of the metaborate of barium, concerning a 

 mixture of which with barium carbonate, Morse and Burton 

 originally said that it " being neither markedly hygroscopic nor 

 capable of absorbing carbon dioxide, can be brought to a con- 

 stant weight more readily than one containing oxide of calcium 

 or magnesium." 



The decomjyosition of hariuni metahorcUe. — That barium 

 metaborate may be decomposed by carbon dioxide in aqueous 

 solution, is proved by my original experiments ; and now is 

 corroborated by those of Morse and Horn. These authors, 

 however, urge that, in alcoholic solutions — TS per cent — the 

 boric acid would be in the form of metaborate of barium 

 only and this should be unattacked to the extent of its insolu- 

 bility. To test this point directly, carbon dioxide was passed 

 into equivalent parts of barium hydrate and boric acid in 78 per 

 cent alcoholic solution. The precipitate gave abundant evi- 

 dence of the presence of carbonate, showing decomposition of 

 the metaborate. The extent of this decomposition was deter- 

 mined quantitatively by determining the carbon dioxide in 

 another similar precipitate. Barium hydrate and an excess ot 

 boric acid in a mixture consisting of 78 per cent alcohol, were 

 treated in the cold for three hours with carbon dioxide. The 

 precipitate was filtered, washed, and analyzed- for carbon 

 dioxide with the following result : 



Ba(OHX taken, 0-7883 grm. ; Bfi, taken, 0-3576 grm. ; 

 excess BJd,, 0-0357 grm.; CO, found, 0-20i2 grm. ; CO, in 

 total barium carbonate, 0-2024 grm. 



Evidently the metaborate of barium in alcohol was completely 

 decomposed by carbon dioxide and the boric acid liberated. 



Another experiment was made as above, except that equiva- 

 lents were taken and the treatment with carbon dioxide was 

 discontinued after thirty minutes. After stopping the flow of 

 carbon dioxide, the mixture was boiled for three minutes, to 

 remove any excess of gas. The precipitate was filtered, washed 



*Tlie italics, as in other quotations to follow, are mine. — L. C. J. 



