THE TECHNOLOGIST. [August 1, 1864. 



2U ON CHEMISTRY APPLIED TO THE ARTS. 



called by him aluniinized charcoal. This he obtained by mixing inti- 

 mately, and heating, finely pulverized charcoal and stdphate of 

 alumina, when he obtained a powerful decolorating agent containing 

 7 per cent, of alumina, and well adapted for decolorating acid solutions, 

 such as those of tartaric and citric acids, in chemical works. He also 

 prepared what he called coal-tar charcoal, by melting one pound of pitch 

 in a cast-iron pot, adding to it two pounds of coal-tar, and mixing 

 intimately with it seven pounds of hydrate of lime, then carrying the 

 whole to a high temperature, allowing it to cool, removing the lime by 

 washing the mass with hydrochloric acid, and then with water, when 

 carbon in a high state of division was obtained, possessing powerful 

 decolorating properties. The following series of experiments by Dr. 

 Stenhouse perfectly illustrate the chemico-physical action of animal 

 black as a decolorating agent. He boiled a certain amount of char and 

 his two charcoals, with a solution of logwood, then treated each black 

 separately with ammonia, when the following results were obtained : 

 Aluminized charcoal yielded no colour. Bone-black -but a slight amount. 

 Coal-tar charcoal, large quantities. But it would be wrong in me to 

 leave you under the impression that animal black can onlj remove 

 colours from solutions. Purified animal black, that is to say, animal 

 black deprived of its mineral matters by the action of muriatic acid 

 and subsequent washing, has the power of removing certain bitters from 

 their solutions. Thus Dr. Hofmann and Professor Redwood applied this 

 property with great skill, some years ago, to the detection of strychnine 

 in beer. Again, Mr. Thos. Graham, Master of the Mint, published a 

 most interesting series of researches, in which he established the fact 

 that purified animal black had the power to remove a great number 

 of saline matters from their- solutions, such as the salts of lime, lead, 

 copper, &c. 



Revivication of Bone Black. — After a certain quantity of syrup sugar 

 has percolated through the cylinders containing bone black, the inter- 

 stices become so clogged with impurities, that it loses its power of 

 decolorating the syrup. Sugar refiners are therefore in the habit of re- 

 storing the power of their bone black, generally speaking, by submitting 

 it to a process of calcination, which volatilizes or destroys the organic 

 .matter fixed by the char. It has been proved by experience that char 

 may undergo this operation about twenty times before its pores become 

 so clogged with dirt as to render it useless. [Here the lecturer described, 

 with the aid of drawings, several of the various apparatus used in sugar 

 refineries for the above process, alluding particularly to that of Messrs. 

 Pontifex and Wood, by which a ton of char is revivified every twenty- 

 four hours.] A new process, however, has been devised by Messrs. 

 Leplay and Cuisinier, which as a whole deserves the attention of refiners, 

 though I am aware that several of the details of their process have been 

 used for some time. The char Avhich has served its purpose in the 

 cylinders, instead of being removed, is treated at once by the following 



