140 ACIDIFIABLE COMBUSTIBLES. 



next bject which engaged my attention 



carbonic wa s, to disengage the carbonic acid from 100 



acid gas de- . & & 



grains of calcareous spar, and collect it over mer- 

 cury, in order to ascertain its volume. This ex- 

 periment appeals so easy, that the reader will be 

 surprised to hear, that a considerable time elaps- 

 ed, and many fruitless experiments were made, 

 before I was able to make it with accuracy. 



The first method that I tried was, to fill a gra- 

 duated glass jar with mercury, to let up into 

 it some muriatic acid, and then to introduce 

 a given weight of calcareous spar. By this 

 method the carbonic acid was extricated with 

 great rapidity ; but the volume of gas obtained 

 was always considerably greater than it ought to 

 have been, judging from my previous knowledge 

 of the specific gravity of carbonic acid gas. The 

 reason I found to be, that a portion of the mu- 

 riatic acid had been disengaged in the form of 

 gas, had mixed with the carbonic acid gas, and 

 had augmented its volume. Thus the gas from 

 100 grains of calcareous spar sometimes amount- 

 ed to 109i cubic inches ; while I knew that the 

 true volume of the gas, if pure, could not exceed 

 94i cubic inches. 



I attempted to prevent this extrication of mu- 

 riatic acid gas, by employing very weak muria- 

 tic acid for dissolving the calcareous spar ; but 

 when the experiment was made in this way, the 

 volume of carbonic acid gas extricated fell al- 



