222 ANNUAL OF SCIENTIFIC DISCOVERY. 



tive matter with excess of silica, which has a tendency to consolidate 

 in a vitreous form, and imprisons gaseous matter in its solidification. 



ON THE CHEAP PRODUCTION OF OXYGEN GAS. 



In a recently published report of Dr. Hoffmann, of London, on the 

 " Chemical processes and products" of the Great Exhibition of 1862, 

 he notices the production and application of oxygen gas in the arts 

 as follows : 



" Of the various processes by which oxygen gas can be produced, 

 I think we may say that two only are now used, viz : chlorate of potash 

 with and without manganese, and manganese alone : the latter is 

 selected only for cheapness when a considerable quantity of the gas is 

 required ; chlorate of potash, with manganese for facility of operation ; 

 and chlorate of potash alone when purity is the principal object to be 

 attained. More recently other processes have been recommended, 

 one of which, by heating together a mixture of nitrate of soda and 

 oxide of zinc, has been patented ; from this mixture oxygen is said 

 to be produced at a cheaper rate than by any other method at present 

 known. Unfortunately for the value of this discovery, the produce 

 is contaminated with a considerable percentage of nitrogen. Mr. 

 Kuhlruan, of Lille, discovered and published an ingenious and beautiful 

 process for the production of oxygen by means of baryta. He found 

 that by passing a current of common air through caustic baryta, heated 

 to dull redness, peroxyd of barium was formed, which, on an increase 

 of temperature, is resolved into oxygen gas and caustic baryta, the 

 latter ready again to perform its part in a similar operation. The idea 

 naturally suggested itself that the means were now at hand for getting 

 oxygen from the atmosphere in any quantity at a small cost. This 

 method, although so promising, has been for the present abandoned. 

 It was found that after a few operations, either from a molecular 

 change or from the silica or other impurities, a sort of glass or fu- 

 sion resulted on the surface, the baryta ceased to absorb oxygen, 

 and the operation ceased. 11 



Should this difficulty be overcome, and the process be made avail- 

 able for supplying oxygen at a cheap rate for manufacturing pur- 

 poses, a great impulse will be given to what is termed furnace 

 chemistry, and our power over the more refractory provinces of the 

 mineral kingdom be proportionately increased. 



As this change in the condition of the baryta in Kuhlman's process, is 

 in the opinion'of Prof. Hoffmann, physical rather than chemical, it is 

 not unlikely that means to remedy the evil may soon be suggested. 



" A cheap process for the preparation of caustic baryta, and its 

 derivative the peroxyd of barium, would probably lead to the ex- 

 tensive manufacture of peroxyd of hydrogen, a compound whose 

 powerful bleaching and oxydizing properties would render it an inval- 

 uable adjunct in many manufacturing processes." The Report goes 

 on to suggest many other applications where success may be ex- 

 pected, and adds : "Nothing, it has been well said, seems so difficult 

 as the invention of to-morrow, nor so easy as the invention of yester- 

 day." 



