102G TiiANSACTTOKS OF THE AMERICAN INSTITUTE. 



will be displaced from the liine and afterward be decomposed into 

 sulphurous acid and oxygen, and that silicate of lime will remain. 

 "We give this method without being able to state what the practical 

 working of it would be. It has never been tried on a large scale, the 

 nearest approach to a trial being in the manufacture of glass. The 

 heat required to fuse silicate of lime alone is very great, and it is 

 probable that oxygen would be liberated much below this point of 

 fusion. If any of our readers try this method we should be glad to 

 hear the results of their. experiments. 



10. A method recommended by Deville, and largely employed in 

 France, is the decomposition of sulphuric acid by heat. At the 

 Paris exhibition of 1867, the plan proposed for the accomplishment 

 of this decomposition was to sufier the sulphuric acid to trickle down 

 upon a highly heated floor of sulphate of alumina, and to pass the 

 sulphurous acid gas through soda or magnesia. 



The sulphate of alumina protected the bottom of the furnace and 

 the incidental sulphurous acid was economized. There are few 

 cheaper methods than this, especially if conducted in connection 

 with sulphuric acid works. 



It is a curious fact that although Deville recommends this method, 

 lie employs the old fashioned process of chlorate of potash whenever 

 he requires oxygen for his laboratory experiments. It goes to show 

 that a convenient apparatus for the preparation of oxygen gas from 

 sulphuric acid remains to be invented. 



11. AVebster has proposed to heat ©ne part of Chili saltpetre and 

 two parts of crude oxyd. of zinc to a point sufficient to accomplish 

 the decomposition of the nitrate of soda. By this method caustic 

 soda and oxyd of zinc are left in the retort. The same oxyd of 

 zinc serves for any number of operations. There would appear to 

 be no waste in this process, but the Chili salti^etre is too valuable for 

 ■other purposes to admit of its employment for this. ■ 



12. It is sometimes required to prepare oxygen for medical uses, 

 and for this purpose it is desirable to have a method for its evolu- 

 tion without the intervention of heat. By employing the binoxyd 

 of barium, the bichromate of potash and sulphuric acid, we are able 

 to liberate oxygen in considerable quantity as easily as we can obtain 

 hydrogen from water by means of zinc and sulphuric acid ; but the 

 materials are expensive. The following equation represents very 

 nearly the reaction that is supposed to take place : 



3 "BaO-"+4nO, SO^'+KO, CrO ==3 BaO, SO-^+KO, HO, S0='+ 

 Cj.2 03+6 0. 



