Action of Ammonia on glowing Charcoal. 281 



Liebig observed, that on heating the bichromate of the per- 

 chloride of chromium with ammonia, or the chloride of chro- 

 mium in gaseous ammonia, metallic chromium is obtained ; 

 the metal obtained, according to these two methods, exhibits, 

 however, very different properties ; the first being a black 

 powder, which, under the steel, acquires a metallic lustre, while 

 the latter has a dull chocolate-brown colour. This difference 

 iu the properties induced M. Schlatter to examine them more 

 accurately : he found, that on heating the brown powder in a 

 combustion-tube, from which atmospheric air had been ex- 

 pelled by means of carbonic acid, a beautiful incandescence 

 ensued, accompanied by a violent disengagement of gas, which 

 proved to be nitrogen mixed with nitric oxide. Another ex- 

 periment showed that the substance contained no hydrogen; 

 it is, therefore, nitruret of chromium. Its composition is re- 

 presented by the formula N 5 Cr 2 . It is impossible to free it 

 entirely from ammonia. The brown powder is a mixture of 

 the nitruret with the oxide of chromium, to obtain it free from 

 which it must be prepared in the following manner : — The 

 chloride of chromium is heated in an atmosphere of hy- 

 drochloric gas, until it is anhydrous; it has then acquired 

 a beautiful peach-red colour, and is deposited in crystalline 

 laminae in the upper part of the tube. On treating it with 

 ammonia all contact with oxygen must be carefully avoided. 

 Thus prepared, the nitruret of chromium is black, and has 

 all the properties of the body prepared after the other method. 

 (Mitscherlich mPoggendorff's Annalen,\o\. xlix. p. 407; Ber- 

 zelius in Journ. fur Prakt. Chem. vol. xxiii. p. 230 ; and 

 Schrotter in Annal. der Chem. und Pharm. vol. xxxvii. p. 129.) 



Action of Ammonia on glowing Charcoal ; formation of Prussic 



Acid, Sf-c. 



In a notice published in Liebig's Ann. der Chem. und Pharm. 

 vol. xxxviii. p. 69, M. Kuhlmann advances the following po- 

 sitions, to which he has been led by experiments on the 

 properties of spongy platinum: — 1. All volatile nitrogenous 

 compounds can, when mixed with air, oxygen, or an oxygen- 

 ous gas, be converted by this means into nitric acid or hypo- 

 nitric acid : 2, the same compounds produce with hydrogen, 

 or an hydrogenous gas, ammonia: 3, mixed with hydrocar- 

 bons, or when the nitrogen compound contains hydrogen with 

 carbonic oxide, they produce prussic acid or the prussiate of 

 ammonia. In repeating the experiment described by Clouet, 

 viz. the production of prussic acid by the action of ammonia on 

 incandescent charcoal, M. Kuhlmann found it to succeed per- 

 fectly, the prussiate of ammonia is obtained however, the free 



