1825.] Mr. Phillips*^ Reply fa Dr^ Christmh, f/Mf 



" Mr. Phillips, on the other hand, proposes to boil the suspected 

 fluid with animal charcOal^ and says, he has found that port vvihe, 

 gravy soup, infusion of onions, or the liquor arsenicaliSf may be 

 rendered in that way sufficiently colourless for the application of 

 the most delicate tests." The author then continues, " these 

 processes do not seem to have been yet subjected to experiment 

 by other chemists. I can conceive no other reason, at least, 

 why the former in particular has been so long under the public 

 eye without notice or criticism ; for no one can have made fair 

 trial of them, without being convinced that their application is 

 confined by such narrow limits, and that, within those limits, they 

 are hable to so many fallacies, as must render them almost 

 entirely useless in medico-legal researches." With Dr. Christi- 

 son's criticism upon Orfila's process I shall not interfere ; but I 

 will freely inquire, whether his remarks upon the method 

 which I propose are entitled to the fairness to which their 

 author lays claim ; and it may be Useful in this investigation to 

 examine how far Dr. Christison is correct upon points on which 

 he can have but little apology for error : this may serve as a 

 guide to determine the value of his experiments, and of the infer- 

 ences deduced from them. 



After stating that the best substance for reducing arsenic* on 

 the small scale is the black flux, he adds in a note, " almost all 

 authors on chemistry and medical jurisprudence recommend, as 

 an alternative, a mixture of charcoal powder and potass." On 

 this subject, I have referred to the following well known authori- 

 ties, viz. Black, Henry, Murray, Paris and Fonblanque, Brande, 

 andUre ; and they mention no other substance than black flux for 

 the purpose of reduction. Duncan and Aikens advise the use of 

 charcoal, or carbonaceous matter ; Beck recommends black flux 

 made of carbonate of potash and charcoal, and the same mixture 

 is advised by Mr. A. T. Thomson ; while Smith and Orfila, as 

 far as I have examined, are the only persons who employ a mix- 

 ture of charcoal and potash. ■^'" 



In the note from which this passage is quoted, there is another 

 assertion which appears to me to be very incorrect ; it is that 

 •' the charcoal of the black flux is not necessary in the process; 

 and subcarbonate of potass might therefore answer as well, biit 

 it is seldom so dry." Now if this were fact, it would be aft ^ 

 important addition to our knowledge, for it would save the intrO^' 

 duction of charcoal into the tube, and prevent it from being 

 mistaken for subUmed arsenic. I did indeed find that whei^ 

 arsenious acid was heated with carbonate of potash, some" 

 metallic arsenic sublimed ; and this arose from the conversion df 

 part of the arsenious acid into arsenic acid, one portion of th#* 

 arsenic taking oxygen from the other.- That this is the triife^; 



* I take this opportunity of stating that I find my method of using an uncoated tulf' « * 

 and a spirit lamp in the process of reduction is not original ; for I have since observed 

 that Mr. Brande recommends the same plan in his Manual. 



