On the Constitution of Chromium- compounds. 313 



Besides these biatomic compounds of diallyle, there is a mono- 

 atomic series, the starting-point of which is the monohydriodate 

 of diallyle, G 6 H 10 HI, obtained from the dihydriodate by the loss 

 of one molecule of HI. 



For the reduction of nitro-compounds, Zinin first introduced 

 the use of sulphuretted hydrogen ; and Bechamp subsequently 

 showed that a mixture of iron filings and acetic acid is an ex- 

 tremely energetic reducing agent. Sulphuretted hydrogen acts 

 in such a manner that a single atom of hyponitric acid, NO' 2 , is 

 replaced by NH 2 ; while acetic acid and iron filings act so that 

 all the NO 2 present is replaced by NH 2 . Beilstein* has recently 

 made some experiments on the reducing action of a mixture of 

 tin and hydrochloric acid. He finds that it's action is very ener- 

 getic ; in all cases the whole of the hyponitrous acid, NO 2 , is 

 converted into the group NH 2 . Thus nitrosalicylic acid is con- 

 verted into amidosalicylic acid, in accordance with the equation 



G 7 H 5 (N0 2 )0 3 + 6Sn + 6HCl = G 7 H 5 (NH 2 )0 3 + 2H 2 0-f6SnCL 



Nitrosalicylic acid. Amidosalicylic acid. 



In a similar manner dinitrotoluole, G 7 H 6 (NO 2 ), is converted into 

 toluylene-diamine, C 7 H 6 (NH 2 ) 2 ; and picric acid, € 6 'H 3 (N0 2 ) 3 0, 

 into picraminef, G G H 3 (NH 2 ) 3 . 



XLIII. On the Constitution of Chromium-Compounds. 

 By J. Alfred WanklynJ . 



THE researches of Deville and Troost on the vapour-densi- 

 ties of the metallic chlorides have led to various attempts 

 to revise the atomic weights of most of the metals. One of the 

 most obvious ways of dealing with the case of iron and of the 

 different metals belonging to the iron family (including of course 

 chromium), was to represent the metal as a six- atomic element, 

 i.e. 



Fe^=ll2; Cr vi =105 



Fed 6 CrCF. 



This view, which has been advocated by several chemists, in- 

 volves, among other inconveniences, a very complex formula for 

 the protochlorides, or else the assumption that the protochloride 

 is an unsaturated compound. 



In a paper published in the spring of 1862 §, Erlenmeyer 



* Liebig's Annalen, May 1864. 

 f Phil. Mag. vol. xxv. p. 540. 

 % Communicated by the Author. 

 § Zeitschrift fur Chem. und Pharm., p. 129. 

 Phil Mag. S. 4. Vol. 29. No. 196. April 1865. Y 



