156 HISTORICAL INTRODUCTION TO CHEMISTRY CHAP. 



tion (loc. cit., p. 442), the carbon being burnt to carbonic 

 oxide, and the hydrogen liberated, thus : 



olefiant gas + oxygen > carbonic oxide + hydrogen 



I VOl. I VOl. <2 Vols. <2 Vols. 



When sparked alone the gas was decomposed into carbon 

 and twice its volume of hydrogen, thus : 



olefiant gas > carbon + hydrogen 

 i vol. 2 vols. 



Olefiant gas was thus shown to contain twice its volume of 

 hydrogen, and enough ca'rbon to give twice its volume of 

 carbonic oxide, or of carbonic anhydride. 



Marsh gas or light carburetted hydrogen. The forma- 

 tion of an inflammable gas during the decay of vegetable and 

 animal "matter was known from classical times, and was 

 noted by van Helmont, who described all such gases as 

 " gas pingue." 



The first accurate work on the subject was that of 

 Volta who showed in 1776 (Letters on the Inflammable Air 

 of Marshes), that whilst the gas from metals and acids 

 required for its combustion twice its volume of air, the 

 MARSH GAS collected from putrid marshes required from ten 

 to twelve volumes. The gas was also examined about the 

 same time by Priestley in England and by Franklin in 

 America. It was investigated very carefully in 1804, by 

 Dalton, who gave to it the name CARBURETTED HYDROGEN. 

 Dalton describes its preparation and properties as follows : 



" It was in the summer of 1804, that I collected at various 

 times, and in various places, the inflammable gas from ponds ; 

 this gas I found always contained some traces of carbonic 

 acid and a portion of azote ; but when cleared of these, it 

 was of a uniform constitution. After due examination, I was 

 convinced that just one half of the oxygen expended in its 

 combustion, in Volta's eudiometer, was applied to the 



