on the Borates of Barium. 53 



mended by Morse and Burton may result in a mixture con- 

 taining barium carbonate and barium metaborate, or barium 

 carbonate, barium metaborate and boric acid, or, indeed, barium 

 carbonate ^ndifree boric acid. Of these compounds, both the 

 barium metaborate and boric acid retain water considerably 

 beyond 100° C. 



Morse and Burton assumed that they had, after evaporation, 

 a mixture containing only barium carbonate and barium 

 metaborate. Morse and Horn explain it as follows : " It may 

 be urged that even if Morse and Burton had the metaborate in 

 insoluble condition, and it had been sensibly attacked during 

 the treatment with carbon dioxide, nevertheless, in the subse- 

 quent attempt to heat the dried residue to constant weight, 

 the metaborate must have attacked the carbonate. It has 

 since then come to light that some caution must be exercised 

 in this part of the manipulation. In the original description 

 of the method, it was simply stated that the residue was 

 heated to constant weight over a triple burner. The practice 

 then, and on the few occasions when the process has since 

 been used, was to hold the burner in the hand and rapidly 

 play the flame over the platinum dish in order to secure as 

 uniform a temperature of the contents as possible. The object 

 in using a triple burner was not to obtain a very high tempera- 

 ture^ which is not necessary, but, rather, to employ a flame 

 large enough to keep the whole dish hot. No difficulty was 

 experienced, when the heating was conducted in this manner, 

 in quickly obtaining constant and correct iveights. Neverthe- 

 less, it must be admitted, the authors of the method did not at 

 that time suppose that the temperature at which the meta salt 

 will attack the carbonate is so low as it has since been found 

 to be. The temperatures employed by Jones were evidently 

 far above those to which Morse and Burton heated their mix- 

 tures of metaborate and carbonate." 



The use of a triple burner to secure gentle and uniform 

 heating is unusual. Indeed, Morse and Horn use it in experi- 

 ment XIY for a quite different purpose, i. e., to secure a tem- 

 perature which decomposed the carbonate and borate mixture, 

 present. That the temperatures employed by me in my 

 original experiments were not ^\far above those" used by 

 Morse and Burton, can be answered best by the words of Morse 

 and Horn : " At a full red heat the meta salt attacks the car- 

 bonate with expulsion of carbon dioxide" (page 130). "The 

 temperature at which a mixture of the metaborate and the car- 

 bonate of barium is stable and which is still sufficiently high 

 to insure the dehydration of the former, appears to be just 

 under a red heat" (page 130). Morse and Horn do not, how- 

 ever, produce any evidence to show that the meta salt is dehy- 



