68 



C. W, R. POWELL. 



The gas analyses show that the greater part of the 

 reaction is taking place according to Equation 1, on an 

 average 93% of hydrogen being liberated to 7% sulphur 

 dioxide (at 30° O.). Hence it might be concluded that this 

 is the initial reaction, and that the nascent hydrogen is 

 only able to reduce a small amount of the sulphuric acid at 

 the temperature of the experiment. This theory would be 

 substantiated by analysing the gases evolved at higher 

 temperatures, and the author is at present carrying the 

 investigation further with this end in view. 



Some preliminary experiments have already been con- 

 ducted, and a few of the results are included to indicate 

 the course of the reaction above 100° O. The percentage 

 of SO 2 rapidly increases, until at 180° C. the amount of 

 hydrogen, if any is present at all, becomes too small to be 

 detected by the ordinary method of analysis. 



Temperature °C. 



SO* 



H 





150 



47 



53 



100-0 



165 



48 



52 



100-0 



180 



100 





100-0 



200 



100 



... 



100-0 



Warner 1 has stated that sulphuric acid is not reduced by 

 hydrogen unless nascent below 160° 0., and from the above 

 table it will be seen that a very marked change in the 

 reaction occurs between 165 - 180° O. 



However, it may be the case that the sulphur dioxide is 

 produced by a direct reduction of the acid by the iron, as 

 has been shown to be the case with mercury 2 — although 

 with copper as has already been referred to, the inter- 

 mediate formation of nascent hydrogen has been definitely 

 proved. 3 The rate of the reaction and the influence of 

 impurities in both the H 2 SO* and the iron upon the reaction 

 are also at present being studied. 



1 Chem. News, xviii, 13, p. 1873. a Loc. cit. 3 Loc. cit. 



