1024 Transactions op tee Aiierivan Institute. 



remarks by many interesting experiments. The following paper 

 was presented : 



On the Manufacture of Oxygen Gas. 



Prof. C. A. Joy. — Althoiigli one-lialf, if not two-tliirrls, of the 

 weic;lit of the globe is made up of oxygen, yet a thoroughly cheap 

 and ])ractlcal method for the manufacture of this gas on a large scale 

 has not been discovered. There is no want of oxygen compounds, 

 but how to decompose them is a difficult problem. We propose to 

 recapitulate some of the most important methods now employed, 

 and from them our readers may be able to select those which will be 

 most available. 



1. The old historical method of heating the red oxyd of mercury 

 and of driving off the oxygen contained in it, is given still in our 

 chemical text-books, and is employed as a lecture room experiment. 

 It is easily enough accomplished, but would be too expensive on a 

 large scale. It may be worthy of note that the original burning- 

 glass which Dr. Priestley used in the first preparation of oxygen was 

 brought by him to this country, and is now preserved in the cabinet 

 of a college in Pennsylvania. One of Priestley's tubes for collecting 

 the gas is in the possession of the eminent American chemist, Dr. 

 "Wolcott Gibbs, of Cambridge. 



2. The chlorate of potash method is more frequently employed 

 than any other. It is a curious fact that in nearly all of the estab- 

 lishments where an effort has been made to introduce a new way of 

 preparing oxygen, all of the gas used for showing the value of the 

 invention has been prepared from the chlorate of potash, and the 

 excuse given is that " our works are not yet in running order, and 

 cannot be until a sufficient amount of stock has been subscribed.*^ 

 After the stock is sold we usually hear nothing more of the inven- 

 tion. 



For all purposes of the lecture room and laboratory the preparation 

 of oxygen from chlorate of potash is the most convenient and eco- 

 nomical. In order to ascertain the amount of oxygen we can make 

 from a given weight of the chlorate of potash, we take the weight of 

 the combinino: numbers and make a rule-of-three statement. For 

 example, how much oxygen can be made from 100 j^ounds of the 

 chlorate, 123, 5 : 48 : : 100 : X. 



It is always well in actual operations to mix a little black oxyd of 

 -^manganese with the chlorate to prevent the too rapid evoltition of 

 kthe gas. 



