Intelligence and Miscellaneous Articles. 77 



ON THE COMBUSTION OF AMMONIA, ETC., BY THE GREEN OXIDE 

 OF CHROMIUM. BY THE REV. J. E. ASHBY, B.A., F.R.A.S. 



1 . For the following experiments, it is necessary to provide a small 

 shallow saucer (such, for instance, as is used to hold a small quantity 

 of any water-colour), and a piece of fine wire-gauze to cover it. 

 Set out also chromic acid, pyroxylic spirit, alcohol, and blotting- 

 paper, and turn up the spirit-lamp to a large flame when required. 



2. I prepare the green oxide of chromium from chromic acid. 

 With a small test-spoon set the chromic acid in powder or very fine 

 crystal upon the wire-gauze, and placing the gauze upon blotting- 

 paper wet with pyroxylic spirit or alcohol, it will change colour, burst 

 into flame, and emit fumes of the green oxide, which are to be avoided 

 as much as possible. Now heat the residue to incandescence over 

 the spirit-lamp ; if necessary, break up the cinders of green oxide 

 into smaller pieces to allow free currents to pass through the gauze, 

 and for each experiment heat the whole to redness before exposing 

 it to the vapours. 



3. Nearly fill the saucer with alcohol or pyroxylic spirit, cover it 

 with the gauze on which is the dry and warm Cr 2 O 3 , and combustion 

 will begin and be kept up for a considerable time. 



4. Immediately after incandescence, place the gauze over the 

 saucer nearly filled with the strongest liquid ammonia, and, as in the 

 former instances, combustion will commence and continue with the 

 evolution of much heat from the Cr 2 O 3 , which presents the appear- 

 ance of a miniature mass of burning coals. This may be shown even 

 by placing the gauze over the mouth of an unstoppered bottle of 

 liquid ammonia; but to ensure success, the solution of ammonia 

 should be of great strength. 



5. I have not had time to examine the products of combustion 

 when ammonia is thus decomposed ; but I think that nitrate of am- 

 monia must pass off in combination with watery vapour. 



6. The green oxide of chromium thus prepared will probably be 

 found to possess, in a modified degree, all the catalytic properties of 

 spongy platinum. 



12 Mornington Road, 

 Regent's Park, London. 



ADDITIONAL OBSERVATIONS ON CATALYTIC COMBUSTION. 



I find that the sesquioxide of chromium, properly prepared, is by 

 far to be preferred to spongy platinum in most cases, and can be 

 made at so trifling a cost that large operations may be cheaply carried 

 on by the use of it. The combustion of ammonia is very singular, 

 and so complete that the strong solution might even be used as fuel 

 for a catalytic ammonia-lamp for distillations, evaporations, &c. 

 Coal-tar naphtha furnishes a very complete and cheap combustible. 

 A friend has tried dry ammoniacal gas fed with oxygen, and the 

 result, as might be expected, is somewhat more brilliant. I now 

 prefer to prepare the sesquioxide by placing chromic acid in fine 



