1868.] Dr. Hofmann on the Mustard Oil of the Ethyl Series. 255 



very probable the existence of a series of bodies isomeric with the sulpho- 

 cyanides. xllready M. Cloez has shown that the action of chloride 

 of cyanogen on ethylate of potassium gives rise to the formation of an 

 ethylic cyanate possessing properties absolutely different from those be- 

 longing to the cyanate discovered by M. Wurtz. On comparing, on the 

 other hand, the properties of the methylic and ethylic sulphocyanides with 

 those of the sulphocyanides of allyl and phenyl, it can scarcely be doubted 

 that we have here the representatives of two groups entirely different, and 

 that the terms of the methyl- and ethyl-series which correspond to oil of 

 mustard, and to the sulphocyanide of phenyl, still remain to be discovered. 

 Experiments with which I am now engaged will show whether these bodies 

 cannot be obtained by the action of the iodides of methyl and ethyl on sul- 

 phocyanide of silver." 



These experiments I have since concluded, but the hopes which I 

 expressed have not been realized. Dry sulphocyanide of silver is much 

 less easily attacked by the alcohol-iodides than the cyanide. The mix- 

 ture, in consequence of the formation of iodide of silver, rapidly turns yellow, 

 but the reaction is not completed without protracted digestion in the water- 

 bath; on submitting the product of the reaction to distillation, the well-known 

 sulphocyanic ethers, discovered by M. Cahours, are obtained. The expe- 

 riment was performed both in the ethyl- and the amyl-series ; the ethers 

 thus produced, when compared with the compounds prepared by distilling 

 sulphocyanide of potassium with sulphethylates or sulphamylates, exhi- 

 bited the same odour, the same boiling-point, and in general the same 

 chemical deportment. 



The failure of these experiments could not, however, shake my belief in 

 the existence of two series of bodies of the composition of the sulphocyanic 

 ethers. It was only necessary to find the method of producing the new 

 isomers. 



I was fortunate enough almost at the very outset to trace the right track, 

 and I beg leave to submit to the Royal Society some of the facts established 

 even now by my experiments. These experiments are intimately connected 

 with some of my older observations. 



More than twenty years ago, when studying the action of bisulphide of 

 carbon on aniline, I discovered a finely crystallized body, which in succession 

 has been designated as Sulphocarbanilide, Diphenylsulphocarh amide, and 

 sulphuretted diphenylurea. About ten years later*, this compound again 

 passed through my hands. I then found that, when submitted to the 

 action of anhydrous phosphoric acid, sulphocarbanilide was converted by the 

 loss of 1 mol. of aniline into sulphocyanide of phenyl. The phenyl-com- 

 pound has the peculiar })ungent odour of the ethereal oil of black mustard ; 

 like the latter it possesses the faculty of fixing the ammonias — so much so, 

 indeed, that I did not hesitate to describe the new compound as the mustard 

 oil of the phenyl series. 



* Proc. of the Roy. Soc. vol. ix. p. 274. 



