160 ACIDIFIABLE COMBUSTIBLES. 



its atomic 2. Dr. Davy found that fluoboric acid gas and 

 ammoniacalgas, combine with each other in the 

 three following proportions : 



(1) 1 volume fluoboric gas ~fc 



> forming a solid salt. 



1 volume ammomacal gas J 



(2) 1 volume fluoboric gas ") _ 



v forming a liquid. 



2 volumes ammomacal gas J 



(3) 1 volume fluoboric gas ~) 



> forming a liquid. 



3 volumes ammomacal gas \ 



It will be shown in the 7th chapter of this treatise, 

 that, in the greater number of gases, a volume of 

 the gas represents an atom. But in ammoniacal 

 gas this is not the case ; two volumes of this gas 

 are requisite to constitute an atom. It is reason- 

 able to conclude from this, that the second of the 

 preceding compounds is the one consisting of an 

 atom of each constituent. We have it, there- 

 fore, in our power to determine the atomic 

 weight of fluoboric acid from it. 



1 volume fluoboric gas weighs 2'3622 or 4-2519- 



2 volumes ammoniacal gas - 1-18055 - 2'125 



M25 is the weight of an atom of ammonia ; con- 

 sequently, 4*2519 is the weight of an atom of fluo- 

 boric acid. The law of Dr. Prout, which will 

 be found to hold in the atomic weights of all bo- 

 dies, shows us that this number is a very little 

 too high. The true atomic weight is undoubt- 

 edly 45 5 consequently, the true specific gravity 



