ACIDIFIABLE COMBUSTIBLES. 



of carbonic acid driven off. A quantity of car- 

 bonate of potash was fused in a platinum cruci- 

 ble, which varied in different experiments, from 

 80 to 100 grains ; and 9 grains of anhydrous bo- 

 racic acid being added, the fusion was usually 

 continued from one hour to an hour and a halfi 

 or in one case, two hours. The loss of weight 

 in the different experiments was not uniform. 

 The smallest loss amounted to 6*8 grains, and 

 the greatest to 8 grains. In these experiments 

 it is obvious, that the greatest loss of weight 

 must be nearest the truth. Even 8 grains, the 

 maximum toss of weight, is a little below the real 

 quantity of carbonic acid which ought to have 

 been displaced. The reason of the variation in 

 these results, and the difficulty of driving off the 

 full quantity of carbonic acid, I take to be, that 

 the boracic acid has a tendency to fall to the 

 bottom of the fused mass, and to remain at the 

 bottom. It is, therefore, difficult to bring the 

 acid and the carbonate into contact, and to keep 

 them in contact till the whole acid enters into 

 combination with the potash and displaces the 

 carbonic acid. I found that I succeeded best 

 when I placed the acid on the surface of the al- 

 kali. 



But let us see what the atomic weight of bo- 

 racic acid will be, if we suppose 9 grains of it to 

 saturate as much potash as 8 grains of carbonic 

 acid. 8:9: : %'75 : 3-09375 = atomic weight 



