47 
In order to avoid as completely as possible access of 
traces of oxygen, the very hygroscopic pentachloride was 
prepared in a narrow tube, and this was transferred bodily 
into the wider tube in which the preliminary heating with 
hydrogen takes place. 
The metal thus obtained was analysed by placing a 
weighed quantity in a porcelain boat and heating it in a 
glass tube in a current of air. The metal takes fire and 
burns brightly to the pentoxide, a small trace of oxychloride 
being usually deposited, existing as impurity in the metal. 
In one instance when the metal was allowed to oxidise very 
slowly, the formation of an indigo -blue-coloured lower oxide 
was first observed ; this afterwards passed into the yellow 
pentoxide on further heating. 
The following analyses were made with metal obtained 
in two distinct operations : 
I. Weight of Metallic Niobium taken 0-3963 gram. 
Niobium pentoxide obtained... 0-5480 „ 
This corresponds to 0-3810 of metal ; or the substance 
contains 96T4 per cent of niobium. 
II. Weight of Metallic Niobium taken 0-3900 gram. 
Niobium pentoxide obtained ... 0*5403 „ 
This corresponds to 0-3790 of metal ; or the substance 
contains 97T8 per cent of niobium. 
That the substance thus prepared is not, as has been 
supposed, a hydride, is shown by the fact that the second 
of the above specimens on analysis was found to contain 
only 0-27 per cent of hydrogen. 
Metallic niobium possesses a steel-grey colour and bright 
metallic lustre. It is remarkable that it is not attacked in 
the cold by hydrochloric or nitric acids, either dilute or com 
centrated, or even by aqua regia. Strong sulphuric acid, 
on the other hand, dissolves the metal quickly, yielding a 
colourless solution. The metal does not take fire in chlo- 
rine gas at the ordinary temperature, but it does so when 
gently heated, with formation of pentachloride and a trace 
