48 
of oxychloride, owing to the unavoidable presence of a small 
quantity of oxygen in the metal experimented with. 
The specific gravity of metallic niobium at 15 5° is 7'06 
as a mean of two well agreeing determinations made with 
half a gram of substance. 
Niobium Trichloride NbCl s . When the vapour of 
niobium pentachloride is passed through a heated glass tube 
it is slowly decomposed, a black deposit of trichloride being 
formed on the sides of the tube. Niobium trichloride is 
generally obtained as a black crystalline crust which pos- 
sesses an almost metallic lustre, and closely resembles in 
appearance that of a film of sublimed iodine. It is some- 
times deposited in long needle-shaped crystals which ex- 
hibit a dichroic lustre. The trichloride is non-volatile, it is 
not deliquescent, nor is it decomposed by water or ammonia, 
but when brought into contact with dilute nitric acid it 
is at once converted into niobic and hydrochloric acids. 
Heated in the air it emits dense white fumes. 
For the purpose of analysis the trichloride, from several 
different preparations, was, in some cases, decomposed by 
nitric acid directly, and in others first fused with sodium 
carbonate and the fused mass treated with nitric acid. 
No. 1. No. 2. No. 3. 
Substance taken 0*2781 ... 0*4406 ... 0*5344 
Nb 2 0 obtained 0*1930 ... 0*3000 ... 0*3611 
AgCl 0*5681 ... 0*9333 ... 1*1218 
Calculated. No. 1 No. 2. No. 3. 
Niobium Nb 46*88 ... 46*68 ... 47*76 ... 47*42 
Chlorine Cl 3 53*12 ... 50*53 ... 52*40 ... 51*93 
100*00 99*21 100*16 99*35 
When the vapour of niobium oxychloride is passed over 
red-hot charcoal in an atmosphere of carbon dioxide no 
change occurs, and the pentachloride is obtained when the 
carbon dioxide is replaced by chlorine. 
A remarkable reaction occurs when niobium trichloride 
is heated in a current of carbon dioxide ; this gas is decom- 
posed, a white sublimate, consisting of oxychloride, is 
