Mineral Sulphur ets, 47 



ment. But I may say, that I am possessed of almost certain 

 evidence that nitrogen is the active agent ; though I must 

 confess, that the theory of the operations is beyond my 

 science. 



5. Ferruginised charcoal can certainly be made for 

 £200 a ton, and as it yields half of its weight of excellent 

 graphite, is it not possible that it may prove valuable as a 

 manufacture, when the worst black lead sells at 2 shillings a 

 pound ? 



6. Imperfect as my information of this subject is at pre- 

 sent, I shall abstain from entering into any speculations 

 on what I have now announced, and shall conclude with re- 

 marking, that the only notice of any similar product which I 

 have been able to find is in an experiment by Doberciner, 

 which I have not at present the means of referring to. 



January, 1845. 



Extract of a Letter from Captain J. Campbell, 2\st Regi- 

 ment M. N. I. 



" With regard to Lieutenant Latter's account of the new 

 French process for treating mineral sulphurets, in your 11th 

 Number, I would remark, that I believe I am correct in 

 stating, that there is no method known in Chemistry for 

 making saltpetre afford oxygen to sulphurous acid gas, upon 

 which the principle of the whole method turns. There 

 seems to be no doubt, from the methodical description given, 

 that the process is instituted in practice, but that some de- 

 ception or concealment must have been practised by those 

 who permitted the operation to be inspected. Does saltpetre 

 at a red heat become decomposed by the contact of carbo- 

 naceous substances, and perhaps by carboniferous gases? It 

 is perhaps probable, that in the same way that the oxygen 

 combines with carbon, so also at a red heat, may the same 

 combinations take place by the contact of sulphurous acid 



