Intelligence and Miscellaneous Articles. 485 



from the atmosphere. The analyses which the author has performed 

 of this chloride leave no doubt as to its nature ; it is composed of one 

 equivalent each of metal and chloride, Cr CI. It consequently cor- 

 responds to a degree of oxidation of chromium as yet unknown, CrO. 



This same substance is formed when a current of hydrogen is 

 passed over green chloride of chromium heated to low redness ; hy- 

 drochloric acid is evolved, and a white crystalline mass remains ; 

 when operating at a higher temperature, this mass fuses, and on 

 cooling presents a fibrous texture. 



Protochloride of chromium prepared by either of these methods 

 has the following properties : — it dissolves immediately in water ; if 

 the water is aerated, and if air be present during solution, the liquor 

 has a green colour, but it is blue when the influence of oxygen is 

 prevented. M. Peligot states that he is acquainted with no sub- 

 stance which is more rapidly altered than this by the contact of 

 oxygen ; so that in order to ascertain its properties it is necessary to 

 operate with water deprived of air by ebullition, and in an atmo- 

 sphere of carbonic acid gas. 



The green solution resulting from the action of air and water on 

 the protochloride of chromium, possesses the singular property of 

 dissolving a considerable quantity of the violet chloride of chromium, 

 with the disengagement of much heat ; this latter body, when pure, 

 is entirely insoluble in water and in acids ; this property of the white 

 chloride, which accompanies the violet chloride when prepared in the 

 usual way, has thrown much uncertainty on the true characters of 

 this latter body, which some authors consider as very soluble in 

 water, and as producing a green solution, while others with reason 

 dispute its solubility. 



When protochloride of chromium has been prepared with the ses- 

 quichloride and hydrogen, it dissolves in water with the evolution of 

 hydrogen ; this decomposition of water, which is not considerable, 

 seems to indicate the existence of a subchloride, which would result, 

 like the subchloride of uranium, from the long- continued action of 

 the hydrogen on the protochloride. 



The blue solution of protochloride of chromium gives with potash 

 a brown precipitate, which is probably a hydrate of the protoxide, 

 corresponding to the chloride ; ammonia gives a similar precipitate ; 

 an excess of ammonia gives a blue solution, which by exposure to 

 the air becomes violet, and eventually red ; monosulphuret of po- 

 tassium precipitates the protochloride of chromium black. 



On pouring a solution of acetate of potash or soda into the blue 

 solution of chloride of chromium, small red transparent crystals are 

 immediately formed, which rapidly collect at the bottom of the vessel. 

 These crystals are spoiled by a few seconds' exposure to the air ; it is 

 however possible to obtain them in a pure state, by a process here- 

 after to be described, and when dry they have the aspect of protoxide 

 of copper. 



These crystals are the acetate of protoxide of chromium, the com- 

 position of which, taking the mean of four analyses which differed but 

 little, is represented by the formula C^H'O^CrO, HO. A dou'ble 

 sulphate of potash and protoxide of chromium gave the following as 



