D. CHEMISTRY AND METALLURGY. 197 



the portion tested was taken from the middle of the bottle 

 containing it. The same impurity, ammonia, was also found 

 in a very large number of other chemicals in the prepara- 

 tion of which sulphuric acid is employed. Professor Storer 

 thinks that the ammonia may get into the acid, partly from 

 the air, partly from the water employed, partly from a re- 

 duction of the nitric acid used in oxidizing the sulphur di- 

 oxide formed in the first stage of the sulphuric manufacture. 

 In fact, he finds by direct experiment that whenever dilute 

 nitric acid is made to act either upon lead or sulphur (as 

 in the leaden chambers of sulphuric -acid works) traces of 

 ammonia are produced. 4 Z>, December^ 1875. 



AMMONIUM NITRITE. 



This extraordinary substance has been reinvestigated by 

 Berthelot, who obtained it by double decomposition from 

 barium nitrite and ammonium sulphate. The filtered solu- 

 tion, evaporated over quicklime in vacuo, yields crystals of 

 the substance desired. It is also formed by the simultaneous 

 reaction upon each other of nitrogen tetroxide, dry ammonia, 

 and oxygen. It forms a white, crystalline, deliquescent salt, 

 having peculiar elastic properties. It decomposes slowly at 

 ordinary temperatures ; at 60 to 70 Centigrade it explodes 

 violently ; under a severe blow it detonates. In solution 

 the salt, anomalously, decomposes more rapidly than when 

 dry ; heated, torrents of nitrogen are evolved. It seems to 

 be one of the least stable bodies known. Aiincdes cle Chimie 

 et de Fhysique. 



ACTION OF NITRIC ACID ON METALS. 



The subject indicated by tlie heading of this paragraph 

 has recently been studied by Mr. J. J. Acworth, who ex- 

 plains some points which have often led to confusing uncer- 

 tainties. Thus nitric acid, acting in the cold on copper, 

 should yield nearly pure nitric oxide, but does not always. 

 Acworth finds that as cupric nitrate accumulates in the solu- 

 tion, nitrous oxide begins to be formed ; and that when the 

 above-named salt becomes sufticientlv abundant the latter 

 gas is given ofi" almost alone. If ammonic nitrate be added 

 to the nitric acid during its action on copper, the gases 

 evolved consist chiefly of nitrogen with nitrous oxide, and 



