54 Jones — Action of Carbon Dioxide 



drated below red heat. In fact, their experimental evidence 

 points the other way : " The experiment of heating the mate- 

 rial, after treatment with carbon dioxide, until the weight fell 

 below that calculated for a mixture of metaborate and car- 

 bonate, and then of exposing it in the air until the weight 

 became very nearly constant, and finally, of removing the 

 slight excess of weight by placing the material over calcium 

 chloride or sulphuric acid, was many times repeated and 

 always with a satisfactory degree of success except in two 

 cases. In these it was suspected that, while some jportions of 

 the material had heen heated high enough to decompose the 

 carbonate^ other portions had not reached the temperature 

 required for the complete dehydration of the metaborate / for 

 it was observed that the weights gained in the air on these 

 occasions far exceeded the calculated deficits." Evidently, the 

 temperatures at which decomposition of the carbonate and 

 dehydration of the metaborate of barium takes place, cannot 

 be far apart when both processes are going on in the same 

 crucible. 



I quote further (page 133) : " In general, it was found diffi- 

 cult, by heating in our bath, to bring the too great initial 

 weight of the material down to that calculated for a mixture 

 of metaborate and carbonate, though in one case (No. XXX) 

 this was accomplished by heating in the bath for three hours 

 over three burners. The temperature on this occasion, how- 

 ever, rose so high that the thermometer was removed." The 

 thermometer used registered as high as 550° C. 



The conditions described above can only be accounted for 

 in two ways, viz : (1) The metaborate has been decomposed 

 by carbonate dioxide, though this treatment was stopped five 

 minutes after the disappearance of alkalinity with phenolph- 

 thalein — and the barium carbonate has not at this temperature 

 been decomposed ; or (2) the metaborate still contains water. 



A combination of both these explanations, doubtless, more 

 nearly expresses the truth. Morse and Horn, however (page 

 134), seem to prefer the latter explanation. " Tliis," they say 

 (i. e., the behavior of the ignited mixture in experiment XXX), 

 "led us to suspect that the temperature at which complete 

 dehydration occurs and that at which the metaborate begins to 

 attack the carbonate cannot be vQvy far apart." 



The experiments made by Morse and Horn in an effort to 

 show how these mixtures can be " quickly " brought to " con- 

 stant and correct weights" are interesting, but not conclusive. 

 They proposed (page 119) " to determine also the effect of 

 exposing these mixtures, after heating, in an atmosphere con- 

 taining carbon dioxide " with the object of finding '' the tem- 

 perature at which it was presumed a mixture of the metaborate 



