M. Ufer on Nitride of Chromium. 279 
Nitride of chromium contains some undecomposed sesquichlo- 
ride which cannot be removed completely by its being heated in 
ammonia. Ufer purified it by an application of an observation 
of Peligot. That chemist found that a very small quantity of 
protochloride of chromium can convert a large quantity of the 
insoluble violet chloride into the soluble modification. Accord- 
ingly by digesting the impure nitride with zinc and hydro- 
chlorie acid, the nascent hydrogen (which does not attack 
the nitride) reduces a portion of the sesquichloride to proto- 
chloride, which then renders the remainder soluble; by wash- 
ing the residue with water, any sesquichloride is completely 
removed. 
The best method of determining the chromium is to convert 
the nitride into sesquioxide by heating it in oxygen. Ufer also 
determined the chromium by fusing the nitride with carbonate of 
soda and nitre, and estimating the chromic acid thus formed by 
obvious methods. The analyses gave as a mean result 79:1 per 
cent. chromium, and 20°9 per cent. nitrogen; agreeing well with 
the formula NCr?, which requires 79°2 chromium, and 20°8 
nitrogen. Schrétter assigned to this substance the formula 
N?Cr°. But it is probable that Schrétter’s preparation con- 
tained some undecomposed chloride. Ufer’s formula for nitride 
of chromium is rendered probable, not only by his analysis, but 
by the mode of its formation, which is further quite analogous 
to the formation of nitride of boron from boracice acid and 
ammonia. 
BO?+ NH?=38HO+BN. 
Nitride of chromium is a black amorphous powder. It has 
the remarkable property (which it shares with analogous com- 
pounds of tungsten) of decomposing ammoniacal gas into its 
constituents when passed over it at a high temperature; and 
in its preparation, towards the close of the operation, there is a 
moment in which the smell of ammoniacal gas is no longer 
perceived, but instead of it nitrogen and hydrogen gases 
appear. 
Nitride of chromium is a very permanent body. It is with 
difficulty attacked by the strongest acids. Heated in the air, it 
is converted into oxide of chromium. It is not attacked by fusing 
caustic potash, nor by fused carbonate of soda; but heated with 
aqueous potash in a sealed tube to 190° it is converted into 
chromate, and when*fused with nitre a deflagration takes place. 
It is dissolved by alkaline hypochlorites with disengagement of 
nitrogen gas. 
When gently heated in a current of chlorine, small explosions 
at first take place, probably arising from the formation of some 
U2 
