TRANSACTIONS OF THE SECTIONS, f07 



On Paracyanogen, a new Isomeric Compound. By J. F. W. Johnston, 

 A.M., Professor of Chemistry, Durham. 



When protocyanide of mercury is heated, cyanogen is given off and 

 a black substance remains. When the salt is perfectly dry, the gas 

 given off is altogether absorbed by potash, and is perfectly pure. Pro- 

 fessor Johnston therefore concluded that the residual black substance 

 was isomeric with cyanogen. Having communicated this view to M. 

 Liebig, an accurate analysis by that chemist confirmed its truth. Pro- 

 fessor Johnston described the principal properties of this remarkable 

 body, which is a very stable compound, but is converted into cyanogen 

 by an elevated temperature, or by heating it with potassium, with which 

 it forms the ordinary cyanide. 



Oh Arsenical Poisons. By W. Heeapath. 



As arsenical poisons are obtained with much facility and their opera- 

 tion is deadly, they are the principal means resorted to by the secret 

 poisoner. It becomes, therefore, essential to the community that every 

 new fact relating to their administration, operation, or detection should 

 be made known. The author is not aware that any well-authenticated 

 case of poisoning by red arsenic had been published till the Burdock 

 case was examined. In this instance the victim, Mrs. Smith, had 

 been buried fourteen months ; upon examination orpiment was found 

 in the stomach, and the body was jjartly converted into adipocire. In 

 prosecuting his experiments Mr. Herapath conceived the idea of identi- 

 fying the poison found with that sold by the druggist to the witness 

 Evans through an impurity he discovered in the poison of the stomach. 

 With this view he purchased some out of the same box, and requested 

 that it might be of the same kind as that sold the prisoner's agent. It 

 was then found that the box contained three different kinds of substances 

 mixed together, white, yellow, and red arsenic, the two former in 

 lumps, the latter in powder, and that it was the powder of realgar 

 only which had been administered, although it was undoubtedly 

 found as yellow orpiment in the exhumed body. In tracing the pos- 

 sibility of change, he found two agents, sulphuretted hydrogen and 

 ammonia, which would convert realgar into orpiment. Now as it is 

 well known that both of these gases are evolved during putrid decom- 

 position, there could be no difficulty in accounting for the change of 

 colour. But, to place the matter beyond all doubt, a direct experiment 

 was made by poisoning an animal with realgar, which after putrefaction 

 became changed, as in the case of Mrs. Smith. The conviction of the 

 prisoner mainly rested on the evidence of a little girl, who deposed 

 that she saw the prisoner Mrs. Burdock put a powder into some gruel 

 and afterwards administer it to Mrs. Smith. 



At the time considerable doubt was entertained of the truth of her 

 evidence from its being invariably precise, even to a word, and also 

 from the difficulty of believing that any person would be so fool-hardy 

 as to mix and administer poison before a child, and that child a stranger. 



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