CHEMISTRY. 185 



slightly. Gold absorbs hydrogen and nitrogen slightly. Silver 

 absorbs 0.289 of its volume of hydrogen, and then presents a 

 beautifully frosted appearance. Oxygen is taken up in the pro- 

 portion of 0.745. Red-hot iron and steel pass hydrogen as readily 

 as platinum does. Scientific American. 



WHAT IS CHARCOAL? 



Mr. W. Skey, in the " Chemical News, 1 ' denies that charcoal is 

 merely impure carbon, and maintains that carbon in charcoal 

 must exist, in part, at least, in chemical combination with the 

 oxygen, hydrogen, and nitrogen, which the latter is known to 

 contain, and which cling to it at high temperatures with a tenacity 

 unknown in any compounds formed among themselves. He sug- 

 gests, therefore, that charcoal is a carbonaceous compound, or 

 more probably a series of such, comprising both acid and basic 

 substances in equipoise, so as to form a neutral salt or salts. The 

 remarkable absorbent capacity of charcoal, under this theoiy, 

 would no longer be assumed as mechanical, but would be ex- 

 plained chemically. For if charcoal consist of carbonaceous salts, 

 the constituents, acid or basic, will be as insoluble in water as the 

 combination, and consequently their affinities will be feeble even 

 for each other, and when other substances present themselves, 

 possessing superior acid or basic properties, they will immedi- 

 ately attach themselves to these supposed constituents of the 

 charcoal. 



ACETYLENE. 



This gaseous compound, the richest carburetted hydrogen 

 known, contains 4 atoms of carbon for 2 atoms of hydrogen. 

 Although this product exists always, but in small proportions, in 

 common coal gas, still M. Berthelot asserts and no doubt with 

 truth that its presence increases materially the brilliancy of 

 common coal gas, owing to the large proportion of carbon it con- 

 tains, and which, by floating in the flame, radiates light and 

 thereby increases its brilliancy. This substance is characterized 

 by giving, with a solution of protochloride of copper dissolved in 

 ammonia, a beautiful coppery precipitate, which is highly explo- 

 sive. Acetylene, also, when mixed with chlorine, and the mixture 

 is exposed to the action of light, or to any flame containing chemi- 

 cal rays, such as those produced by the combustion of magnesium 

 or sulphuret of carbon, gives rise to violent explosions, with the 

 production of hydrochloric acid and a deposit of carbon. This 

 fact will be a means of distinguishing this substance from another 

 one, which is the chief illuminating constituent of coal gas, and 

 called ethylene, or heavy carburetted hydrogen. Acetylene does 

 not exist merely in coal gas ; M. Berthelot has proved it to exist 

 in a great number of instances, and to be a constant product of 

 the slow combustion of most organic substances. 



Further, this substance offers a peculiar interest, for it is the 

 first ever produced by chemists by the direct union of carbon and 

 hydrogen. Up to the time of this discovery, chemists were ac- 



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