450 Dr. Iitglis 071 the Electrical Conducting Puiver of Iodine. 



what would be in general an imaginary value of a^, if a and a; 

 were real and posllive. But I have already occupied too 

 much space, and need not labour these arguments, for Pro- 

 fessor De Morgan does not materially differ from me here. 

 He seems to regard the ordinary theory as an edifice com- 

 plete in itself, but is content to receive my results as an ex- 

 tension which may prove useful, wheieas I regard them rather 

 as the erection of a wing, required for symmetry, if not for use. 



LXXXIII. On the Conducting Po'wer of Iodine for Electricity. 

 ^3/ James Inglis, M.D.* 



[Addressed to the Chemical Section of the British Association.] 

 IT may not, perhaps, have escaped the notice of some of the 

 ■'- members of this Section, that in extracts from a Prize Essay 

 of mine, published some months ago, in the Philosophical Ma- 

 gazine, I stated that I had found iodine to be a conductor of 

 electricity. Nor may the experiments of Mr. Solly tending to 

 prove the contrary have passed by unobserved. Nevertheless, 

 being satisfied in my own mind what I had published was correct, 

 1 determined at the earliest opportunity to resume the investiga- 

 tion, and instead of answering that gentleman directly through 

 the medium of the Philosophical Magazine, I thought it might 

 be better to lay before you the result, in as much as I shall by 

 experiment prove mj' former statement, and then furnish you 

 with that portion of iodine which you have seen conduct, that 

 you may for yourselves judge of its purity. 



In Mr. Solly's first paper, no mention is made of experi- 

 ments performed with fused iodine ; but his attention being 

 drawn to the subject by a note of mine, he published a second, 

 in which he throws a doubt on the purity of the iodine I had 

 used, saying that it contained " most probably the iodide of 

 iron, which is not unfrequently present in the iodine of the 

 shops." (Lond. and Edinb. Phil. Mag., No. 4.8. p. 401.) 



The iodine I used was obtained from the manufactory of 

 Mr. Whitelaw of Glasgow, where no iron vessel is ever em- 

 ployed, and in which, in its veriest impurity, no iron can be 

 detected. Here, for instance, is one tube containing an 

 aqueous solution of ioduret of iron ; a second, an aqueous 

 solution of the iodine to be tested ; and a third having in it a 

 solution of the ferrocyanate of potassa. Now, on adding 

 a small portion of this last solution to the one containing iron, 

 immediately the blue ferrocyanate of the jieroxide of iron re- 

 sults. But no such effect is produced when the test is added 



* Read before tl'.e Chemical Section of the British Association at Bristol, 

 Aug. 26, 183(j: and now comniunicatcd by the Author. 



