71 249 



with each other, having on an average a volume of about 71 ";» of carbon dioxide 

 and 26 "lu of sulphuretted hydrogen plus hydrogen gas. One of the gas samples 

 from Hengill lias a slightly greater percentage of carbon dioxide but the spring 

 from which this sample was taken differed in other respects also from the 

 surrounding springs. The gas sample Krafla No. 2 is also consistent with spring 

 gases of this type, and as one of Christensen's gas samples is of a similar 

 composition, one has reason to suppose that spring gases with about 71 "/o of carbon 

 dioxide and about 26 "/u of sulphuretted hydrogen plus hydrogen gas, are common 

 among the Icelandic solfataras and mud pools. 



In spring gases of this type, the amount of sulphuretted hydrogen and of 

 hydrogen gas, taken separately, may each vary considerably, but taken as a whole, 

 the percentage of the volume of these two gases is fairly constant. In his remarks 

 on the spring gases from Krafla, Christensen mentions that an increase in the 

 amount of sulphuretted hydrogen is attended by a decrease of the amount of 

 hydrogen gas. It appears thererefore that the sulphuretted hydrogen and the 

 hydrogen are closely related to each other in the spring gases. Christensen is of 

 tbe opinion that an easy explanation of this is found in Bunsen's theory of the 

 process of formation of hydrogen and sulphuretted hydrogen in the hot springs, 

 viz. that the sulphuretted hydrogen originally formed disunites according to the 

 formula SHn = Hr, + S. Thus, a molecule of hydrogen gas is formed by the de- 

 composition of every molecule of sulphuretted hydrogen. 



The hydrogen liberated by the decomposition of the sulphuretted hydrogen 

 does not therefore combine with other substances. As the relation between the 

 volume of the carbon dioxide and the sum of the volumes of hydrogen gas and 

 sulphuretted hydrogen is practically constant in this kind of spring gases, it appears 

 probable from the above that there is a certain connection between the carbon 

 dioxide and the sulphuretted hydrogen before its dissociation. 



Taking into account the laws of chemical equilibrium, we perceive that the 

 cause of the relation which exists between the two gases is either that they are 

 produced in the same place, and consequently under the same chemical and physical 

 conditions, or else that the one gas has liberated the other by acting on its chemical 

 compounds. For it is highly improbable that two gases produced independently 

 in two difTerent places should be found mixed in the same proportion in several 

 separate localities. The possibility that sulphuretted hydrogen, more or less dis- 

 sociated, should always liberate carbon dioxide in the same proportion to the sum 

 of the volumes of hydrogen gas and sulphuretted hydrogen, can hardly be con- 

 sidered, as it does not harmonize with the laws of chemical equilibrium. 



In mj' opinion , the foregoing experimental data seem to indicate that the 

 three gases, carbon dioxide, hydrogen and sulphuretted hydrogen, are produced at 

 the same time and by the same physical and chemical processes. 



The conditions of the production of these gases must consequently be the 

 same over vast stretches of Iceland. Most probably the source of gas evolution is 



