390 Transactiom. — Chemistry. 



stimulates me to this action is, that so far as opinions upon it are antagonistic 

 to the one I hold, my researches upon the subjects connected with it are either 

 not taken into proper account, or else are completely ignored. 



Thus the Rev. Mr. Highton, in communicating the fact instanced to the 

 British Association, sitting at Brighton in 1872, referred the origin of the gas 

 evolved to a decomposition of a portion of the sulphuric acid used, the con- 

 stituents of this acid being, as he considered, hydrized to water and sulphu- 

 retted hydrogen by the nascent hydrogen liberated in the carbon pores 

 during the process. 



This statement, though eliciting much discussion at the meeting instanced, 

 did not induce any one there to attempt the application of these published 

 researches of mine thus indicated to the explanation of this phenomenon, but 

 the majority of those who took part in this discussion sought rather to 

 attribute this evolution to the decomposition of sulphide of iron in the 

 graphite used, this substance being in fact a general constituent of graphite, 

 and easily decomposed by sulphuric acid with liberation of the gas mentioned. 



Both these assumptions appearing to me not only radically erroneous, but 

 altogether superfluous, in face of the facts described in the published paper of 

 mine instanced, I ventured in the " Chemical News "* to refer the Rev. Mr. 

 Highton to these facts, and to suggest that the phenomena in question could be 

 easily explained by taking these into proper consideration, and I received an 

 answert from that gentleman^ which, except for certain suggestions, does little 

 more than inform me that his opinions on this subject are unchanged. 



This is the precise position of the question in dispute between us, and as it 

 appears of some importance, from a chemical point of view, and may be also in 

 connection with the very desirable object of freeing coke from sulphur, I now 

 beg leave to treat the whole of it in a paper to you, such a course allowing me 

 to discuss it at greater length and with more justice to myself than can well 

 be attained within the limits which a correspondence column would necessarily 

 impose upon me. 



It will be seen, then, that there are three theories propounded for explaining 

 the evolution of sulphuretted hydrogen from graphite or carbon under tlie 

 circumstances named : — 



(1.) The decomposition of sulphuric acid. 



(2.) The decomposition of sulphide of iron present in the graphite or 

 carbon itself. 



(3.) The removal of absorbed sulphur from the graphite or carbon by aid 

 of nascent hydrogen. 



In relation to the first, I have ascertained that the gas in question is not 

 evolved from carbon when paired with zinc in pure sulphuric acid, if only the 

 • Vol. XXVIL, p. IIG. +Vul. XXVIL, p. 152. 



