IS] 9.] the different Species of Pit -Coal. ] 



air, which was found in the residual gas, must have been sup- 

 plied in the tubes bv an equal volume of the ga* extricated by 

 the decomposition of the coal. Now this gas was a mixture ot* 

 1 1 parts in volume of carbonic acid gaa and one part of azotic 

 p.as ; so that to the volume ot carbonic acid gas evolved, we 

 must add -K-ths of 0*673 cubic inch = 0*616 cubic inch: and 

 to the volume of azotic <ras ^th of the same quantity = 0*066 

 cubic inch. Hence the quantity of carbonic acid and of azotic 

 £as evolved bv the decomposition of a gram of caking coal was 



as follows : 



Cubic inches. 



Carbonic acid gas 5*9327 



Azotic gas 0-5040 



During the process, the tube containing the muriate of lime 

 had increased in weight 0-3744 grain, which is equivalent to 

 0*0416 grain of hydrogen. 



These are the data from which the constituents of caking coal 

 are to be estimated. They are the result of several experiments, 

 which agreed exactly with each other in the quantity of water 

 formed, but not in the quantity of gas evolved. 



One hundred cubic inches of carbonic acid gas. wlien the 

 barometer stands at 30 inches and the thermometer at 60°. 

 contain 12*647 gr. of carbon ; therefore, 5*9327 cubic inches of 

 this gas contain 0*7503 gr. of carbon. 



One hundred cubic inches of a.-otic gas, under the mean tem- 

 perature and pressure, weigh 29*652 gr." therefore, 0*604 cubic 

 inch weigh 0*1494 gr. 



We have, therefore, the constituents of a grain of caking coal 

 as follows : 



Carbon 0*7503 



Hydrogen 0-04 16 



Azote 0*1494 



Ashes 0-0150 



0-9663 



boss 0*0437 



1*0000 



This loss we must consider as oxygen. Had it been any 

 thing else, it would have made its appearance among the gaseous 

 products. 



The weight of an atom of carbon is 0-75, and the weight of an 

 atom ot' hydrogen O 125 ; or an atom of carbon weighs six tunes 

 as much as an atom of hydrogen ; but the number 7503 denoting 

 the weight ot carbon in the coal, is IS times as great as the 

 number 416, which denotes die weight of the hydrogen. It is 

 obvi-ms from this, that the coal contains three times as manv 

 atoms of carbon as it does of hydrogen. 



It we compare the volume Of carbonic acid gas evolved with 



5 



