1825.] Mr, Faraday on a Compoutid of Iodine and Carbon. 15 



DEAR SIR, Royal Institution, June 9, 1825. ' 



I RECEIVED the substance you refer to in your note a day or 

 two ago from Mr. Brande, and have examined it so far as to be 

 able to say it is not the hydriodide of carbon which I made. 

 With reference to its being an iodide or an hydriodide of carbon, 

 I am not quite so sure. It is I perceive the same substance as 

 was shown to me by Mr. Cooper, I should think, two years or 

 more ago, and which he obtained during the preparation of 

 iodine in large quantities. Mr. Cooper considered it at that 

 time as an iodide of carbon, analysing it by passing it over 

 oxide of copper. I saw many of his experiments, but wac not 

 quite convinced that it contained no hydrogen. I know he 

 intended to publish his experiments, but have heard nothing of 

 them since. 



The number of iodine is so high, and the number of hydrogea 

 so low, that it is very difficult to detect and confirm the exist- 

 ence (or to disprove it) of one proportional of the latter in com- 

 pounds of the former ; a proportional of hydrogen coming within 

 the hmits of probable errors in experiment. . I am of opinion 

 that the compound you sent me contains hydrogen ; indeed I 

 am certain of it, for when distilled in contact with, and over 

 heated zinc filings, a gas is evolved which is combustible, and 

 contains hydrogen; but whether this substance results in conse- 

 quence of its existence in the compound, or whether it is due to 

 adhering moisture, is more than I could say without entering 

 into a course of precise experiments. It appears to me also to 

 resemble the hydriodide of carbon which Serullas obtained.—' 

 (Ann. de Chim. xxii. 172, or Journal, xv. 297.) 



I am, dear Sir, yours very truly, 

 J. G . Children, Esq . M.Faraday, 



Article III. 



Facts proving the Efficacy of ISir H. Davy^s Method of protect- 

 ing the Copper of Ships by Electrochemical Action. Extracted 

 from the Letters of a Correspondent, and Dr. Stewart Traill. 



1. The Carnebrea Castle, an Indiaman, belonging to Messrs. 

 Wigram, of 650 tons burden, was protected last spring by a 

 quantity of iron in four portions, two on the bow, and two on the 

 stern, equal to from y^ to yJ-u P^'^^* ^^® ^^^^ since made the 

 voyage to India, and was for some time in the Ganges. 



She appeared bright and clean during the whole of the 

 voyage out and home ; some mud collected on her bottom in the 

 Ganges ; but immediately disappeared when she began to sail. 

 She was put into dry dock about a fortnight ago, and her bottom 



