Mr. Grhtin on an Improved Method of Preparing Oxygen Cras. 46 



of black oxide of copper and chloride of potassium. The latter can 

 be removed by washing, and the former recovered for a repetition of 

 the process, for which it serves any number of times; so that the use of 

 the oxide of copper does not increase the cost of the oxygen gas. 



According to the experiments of Berzelius, 1 grain of chlorate 

 of potash gives -3915 grain of oxygen. Estimating the weight 

 of 1 cubic inch of oxygen gas at '34 grain, this product is equal 

 to M51 cubic inches. I find that 2 grains of the black mixture 

 above described, containing 1 grain of chlorate of potash, give just 

 this quantity of oxygon gas. Hence it appears, that, in this process, 

 the chlorate of potash is completely decomposed, and its oxygen en- 

 tirely discharged in the state of gas ; while, notwithstanding the incan- 

 descence that occurs, the black oxide of copper remains unchanged in 

 composition and properties. 



Cost of Oxygen Gas Prepared by this Process. — If grain (1*75 grain) of 

 the black mixture produces 1 cubic inch of oxygen gas. This quantity 

 of the mixture contains '875 grain, or the 8000th part of 1 lb. avoir- 

 dupois, of chlorate of potash, the market price of which is at present 

 4s. per lb. Hence the cost of the gas is as follows : — 



8000 cubic inches for 4s. 

 1000 — for Gd. 



1 imperial gallon for lid. 



1 cubic foot for 10 J d. 



Advantages of this Process. — It is easy to obtain materials of such 

 a quality as always to ensure the prompt production of pure gas. 

 Excepting a trace of chlorine and a little sublimed salt, both of 

 which arc absorbed by the water of the pneumatic trough, the oxygen 

 gas produced by this process is free from all impurities, especially from 

 carbonic acid ; one economical advantage of which is, that it can be 

 used for many class experiments, largely diluted with common air. 

 No apparatus is required except^ a small glass tube, which is not 

 injured by the operation. There is no expense incurred for fuel, no 

 dirt produced, and no danger to be apprehended. 



The process is not only of easy and rapid execution, but is one that 

 can be always depended upon, so as to save loss of time and materials. 

 When any quantity of oxygen gas is required, it is only necessary to 

 guage the vessels that are to bo filled, and to weigh off 1*75 grain of 

 the black mixture for every cubic inch of gas required. The cause 

 of this certainty in the result is the remarkable incandescence which 

 takes place when the mixture is heated. This ensures the prompt and 

 total decomposition of every particle of the chlorate of potash submitted 

 to experiment! 



It is convenient to mark upon the bottle in which the black mixture 

 is kept, the weight of it necessary to be taken for the purpose of BUing 



