CJiemistry. W^ 



I had occasion to remark that a considerable but variable proportion of 

 pure oxygen gas was always emitted. In one case a stick of forty grains 

 in weight yielded 200 grain measures during solution, although in general 

 the quantity was considerably less. The effervescence was similar to what 

 a slight admixture of peroxide of potassium would occasion. There ap- 

 peared to be vsome connection between the amount of oxygen and the quan- 

 tity of brown insoluble impurities remaining after the solution of the potash. 

 It is probable that the peroxide of iron, from the iron vessels employed in 

 the manufacture of caustic potash, contributes either directly or indirect- 

 ly to the production of the phenomenon. A knowledge of the fact may 

 occasionally be useful, as previous to its detection a series of results in 

 gaseous analysis was vitiated by it." 



10. Composition of NiU-ic Acid. — The 12th volume of the Annals of Phi- 

 losophy, O. S. (p. 351) contains the translation of a paper on the compo- 

 sition of nitric acid, by Eerthollet. The process employed was that of de- 

 composing nitrate of potash by heat in a porcelain retort, the weight and 

 nature of the gaseous products and of the residual potash being ascertained. 

 From these experiments the author concluded that nitric acid is composed 

 of 69.G oxygen + 30.4 azote, instead of 74.08 of the former, and 25.92 of 

 the latter element, as now generally admitted. 



Dr Thomson observes, that, though he has no doubt of the inaccuracy 

 of Berthollet's analysis, he cannot pretend to account for the fallacy. Hav- 

 ing lately prepared some oxygen gas by decomposing nitre, Mr Phillips 

 found that the last gaseous product, if not entirely azotic gas, contained 

 so little oxygen that it extinguished a candle. Upon pouring water into 

 the gun-barrel to remove the potash, he found that oxygen was immediate- 

 ly evolved, and in such quantity that an ignited stick was immediately in- 

 flamed ; and the combustion continued for a considerable period. 



Now BerthoUet distinctly, though erroneously, reports, that the potash 

 retains no oxygen : but it is evident from the experiment now stated, that 

 peroxide of potassium is formed; and it appeared probable to Mr Phillips, 

 that the quantity is sufficient to supply the deficiency of about 4^ per cent 

 of oxygen in Berthollet's experiment. — Fhilos. Magazine and Annals of 

 Philosophy for April. 



11. Nitrification. — In a letter to M. Longchamp, published in the 34tli 

 S'ol. of the An. de Ch. et de Physique, M. Gay-Lussac has defended the old 

 theory of nitrification against the objections of the former chemist, of 

 whose views we gave a short notice in the preceding number of the Jouv' 

 nal. M. Longchamp has endeavoured to establish the two following 

 points. 1. That nitric acid and its salts are generated in substances, or in 

 places, which contain neither animal nor vegetable matters, and which have 

 never been exposed to the emanations from animals. 2. That nitric acid 

 is formed exclusively by the elements of the atmosphere. With respect 

 to the first position, M. Gay-Lussac denies that it is supported by any 

 decisive fact. He has shown that different kinds of chalk, and other cal- 

 careous substances in whlcli nitrate of lime is gradually formed, and which 



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