404 OLEFIANT GAS. 



5. MODE OF ESTIMATING ITS COMPOSITION. 

 (a.) If too little oxygen be used, charcoal precipitates unburnt, 

 and the volume of the residue is greater than that of the original 

 gases. 



(b.) Upon the same principles of calculation as those upon which 

 the composition of the light carburetted hydrogen gas was determin- 

 ed, it follows that in 100 cubic inches there are 



Charcoal, 25.38 85.63 grains, 100. 

 Hydrogen, 4.26 14.37 " 16.71 



29.64* 100.00 116.71f 



(c.) Olefiant gas has therefore 100 grains of charcoal united to 

 16.71 of hydrogen, while the light carburetted hydrogen has the 

 same weight of carbon, with 33.41 of hydrogen, just double ; in 

 other words, the carbon being given, it has half the hydrogen, and 

 the hydrogen being given, it has double the carbon. 



6. CONSTITUTION. 



As, in the combustion of olefiant gas, 3 vols. of oxygen disappear, 

 water is formed, and 2 vols. of carbonic acid are produced, it is evi- 

 dent that as oxygen does not change its volume by combining with 

 carbon, to form carbonic acid, 2 volumes of the oxygen have gone 

 into the carbonic acid with 2 volumes of carbon ; the other volume 

 of oxygen has formed water, and as two volumes of hydrogen are 

 demanded for this purpose, it follows that each volume of olefiant 

 gas contains 2 volumes of carbon, -f-2 volumes of hydrogen, =2 

 equivalents of each. The compound will therefore weigh 12 -f 2 = 

 14, its equivalent.J 



If 2 grains of sulphur be heated over mercury, with 1 cubic inch 

 of olefiant gas, 2 cubic inches of light carburetted hydrogen will be 

 obtained, and charcoal precipitated. Ure. 



7. MISCELLANEOUS.^ 



(.) In olefiant gas there is so large a proportion of carbon, that 

 when a jet of the flame is permitted to play against a white earthen 

 plate, it covers it with charcoal, and the jet burning freely in the air, 

 emits a column of lamp black. 



(b.) Olefiant gas is decomposed by electricity ; and by ignition in 

 porcelain tubes ; products, charcoal and hydrogen, the latter in a 

 volume double -to that of the gas decomposed. 



In the experiment with the tube, by varying the heat, we can 

 cause it to deposit more or less charcoal. 



* Dr. Turner states this number at 29.65, and that for two volumes of hydrogen 

 at 4.23. t See p. 403, (4. &.) JHenry, Vol. I, p. 425, 10th Ed. 



The action of chlorine and iodine upon the carburetted hydrogen gases, will be 

 considered under those heads. 



