1 1028 Transactions of the American Institute. 



converted into the Linoxyd of barium, and then to drive off' the 

 oxygen at a higlier temperature. It was supposed that tlie same 

 portion of baryta would answer for an indefinite number of opera- 

 tions. It is found, however, in an actual experiment, that the pores 

 of the baryta become stopped up, and that tlie operation ceases after 

 a few trials. This objection has been remedied to a considerable 

 extent by' adding caustic soda, or manganese, to the baryta, and it is 

 then said to be highly successful, 



18. The subchloride of copper, when exposed to the air, absorbs 

 oxygen, and this oxygen can be again dispelled by heat. The reac- 

 tion can be represented by the the following equations : 



Cu2 Cl+Cu+air=Cu Cl-fCuO, and Cu CH-CuO+400 degrees 

 Fahrenheit, Cu-^ Cl+0. 



This process, recommended by Mallet, has been highly commended 

 by scientific journals, and companies have been organized for work- 

 ing it. It is probably one of the best thus far proposed. 



19. The method of Tessie du Motay, for the preparation of oxy- 

 gen on a manufacturing scale from the atmosphere, by the interven- 

 tion of caustic soda, black oxyd of manganese, and super-heated 

 steam, has lately attracted a great deal of attention. A small working 

 model of the apparatus required in its preparation was exposed at 

 the Paris exhibition of 1867. The tlieory of this process is that the 

 caustic soda of manganese in a current of dry air becomes manganate 

 of soda and water, and that super-heated steam reconverts the man- 

 ganate into caustic soda and binoxyd of manganese, and liberates 

 the oxygen. The oxygen is separated from the steam by the conden- 

 sation of the water. It is said that the same materials can be 

 employed for the preparation of an indefinite quantity of gas. A 



' company has been organized for the working of this patent in [N^ew 

 York, and if they can succeed in manufacturing oxygen at a cheap 



t rate, they will confer a great boon upon the community. 



We have thus hastily described nineteen processes which are some- 

 times employed in the preparation of oxygen gas. We do not pre- 

 tend to have exiiausted the subject, but have simply aimed at com- 

 prising in one list the best known methods. The process from sul- 

 phuric acid, and the three latter methods, from the- atmospheric air, 

 must be regarded as the most important for application on a large 

 scale. For laboratory use, and until better means are offered, the 

 old way of preparing oxygen from chlorate of potash will retain its 

 supremacy. 



