GEOPHYSICAL LABORATORY. 141 



VOLCANIC GASES. 



The gases which emanate from the lava basin at Kilauea have been 

 found on analysis to consist primarily of free sulphur, free hydrogen, 

 CO2, SO2, CO, H2O, and N2 in varying proportions, but the limits of 

 variation are such as to indicate that the chief gas-reactions which are 

 taking place there are these: 



1. 4CO+2S02^=^4C02+S2 (a) 2CO-I-S2— -^2C0S. 



2. 4H2+2S02^=^4H20+S2 (a) 2H2S^i:^2H2 + S2. 



3. H2+C02^i:^H20+CO. 



At the outset of our investigation of these gas relations, the water- 

 gas reaction (3) had been studied (Haber) and could be accounted 

 estabhshed. The dissociation of hydrogen sulphide (2a) had also been 

 detemiined, but the literature bearing on the other reactions was mea- 

 ger and contradictory. Some of the chemical constants of SO2 were 

 also unknown, so that it was quite impossible to calculate, even approxi- 

 mately, the reactions 1 and 2. The paucity of our knowledge of a gas 

 so important, both scientifically and technically, as SO2, indicated at the 

 outset that many difficulties lay in wait for the investigator in this field. 



In passing it may also be noted that a successful study either of 

 reaction 1 or reaction 2 would render feasible a calculation of the other 

 with a fair degree of accuracy and also would give the much-desired 

 data concerning SO2. 



After preUminary investigation, the reduction of SO2 by CO, i. e., 

 reaction 1, was selected for study, for the reason that it seemed to 

 present less experimental difficulty than the other, and also because 

 it is itself the basis of many of the sulphur-recovery processes used in 

 the industries and is therefore not altogether unfamiliar. 



The usual analytic methods were not immediately applicable, never- 

 theless, for while methods of detecting small amounts of the gases 

 involved are known, they are not suitable for the accurate determina- 

 tion of their amounts. The necessity which thus arose for the develop- 

 ment of new methods and apparatus had to be met before any advance 

 could be made upon the real problem. 



From the nature of gas-reactions it is evident that great difficulties 

 will always attend the procuring for analysis of volcano-gas samples 

 which can be assumed to retain the original composition which they 

 had in the reaction-chamber at the high temperatures there prevailing. 

 There is also the difficulty of differentiating between changes due to 

 cooling and those due to catalysis when it happens that these changes 

 are in the same direction, as in reaction 1. Fortunately, it was found 

 that they are not in the same direction in the case of the subsidiary 

 reaction 



(la) 2CO+S2^=i2COS. 



Studies of mixtures in which this reaction participates are therefore 

 competent to clear up this phase of the problem. 



