THE TECHNOLOGIST. [Sept. 1, 1864. 



94 



<£nmspta*. 



THE CHEMISTRY OF COLOUR.— RESTORATION OF VIOLET. 



TO THE EDITOR OP 'THE TECHNOLOGIST.' 



Sir, — Your readers may probably be interested in tbe following 

 description of a process for restoring tbe colour to violet silk, after its 

 extraction by acid. It is well-known that spirits of hartshorn will act 

 upon black under similar circumstances, but I am not aware that any 

 chemical agent has hitherto been put forward, as a restorer of violet ; 

 and I claim to be the originator of the experiment, with the result of 

 which I am very well pleased. After applying to several chemists and 

 druggists on the subject, and failing to hear of anything that would 

 answer the purpose, it occurred to me to try the " iodine process," which 

 is employed for the purpose of obliterating blots of marking ink from 

 linen ; although the process is doubtless well-known to most of your 

 readers, it may be as well to describe the plan adopted : — First, brush 

 with tincture of iodine the portion of fabric affected ; after a few 

 seconds well saturate the spot with a solution of hyposulphite of soda, 

 and dry gradually in the air ; the colour will then be perfectly restored. 

 I should be veiy glad if any of your correspondents who may try the 

 experiment would give the result through the medium of your 

 columns. 



I am, Sir, yours obediently, 



M. A. B. 



P.S. — I should have stated that I was induced to try the experiment 

 described above, in consequence of my knowledge of some of the 

 chemical properties of iodine, and its relation to the colour in question ; 

 indeed, it is well-known that " iodine " derives its name from the violet 

 vapour which it exhales when volatilized. 



Imntifit Snfoa. 



New Artificial Fuel. — At a meeting of the Franklin Institute 

 recently held in Philadelphia, Professor Flenny exhibited samples of 

 new artificial fuel and gas material, the invention of Mr. "Wm. Gerhardt. 

 This invention consists in preparing porous bricks, balls, or otherwise 

 shaped fire-proof material, which are fully saturated with gas-tar, coal- 

 oil, or any other hydrocarbon of a similar nature. These bricks are 

 afterwards dried and used for the purpose of producing illuminating 



