A NEW CONSTITUENT OF THE ATMOSPHERE. 203 
ings, also heated to bright redness by means of a long-flame burner. H contained 
phosphoric anhydride, and I soda-lime. All joints were sealed, excepting those 
connecting the hard-glass tubes E and G to the tubes next them. 
The gas-holder A having been filled with nitrogen, prepared by passing air over red- 
hot copper, and introduced at C, the gas was slowly passed through the system of 
tubes into the gas-holder B, and back again. The magnesium in the tube G having 
then ceased to absorb was quickly removed and replaced by a fresh tube. This tube 
was of course full of air, and before the tube G was heated, the air was carried back 
from B towards A by passing a little nitrogen from right to left. The oxygen in the 
air was removed by the metallic copper, and the nitrogen passed into the gas-holder 
A, to be returned in the opposite direction to B. 
Fig. 4. 
D (by 
as 











ly 




In the course of about ten days most of the nitrogen had been absorbed. The 
magnesium was not always completely exhausted ; usually the nitride presented the 
appearance of a blackish- yellow mass, easily shaken out of the tube. It is needless to 
say that the tube was always somewhat attacked, becoming black with a coating of 
magnesium silicide. The nitride of magnesium, whether blackish or orange, if left 
for a few hours exposed to moist air, was completely converted into white, dusty 
hydroxide, and during exposure it gave off a strong odour of ammonia. If kept ina 
stoppered bottle, however, it was quite stable. 
It was then necessary, in order to continue the absorption, to carry on operations 
on a smaller scale, with precautions to exclude atmospheric air as completely as 
possible. There was at this stage a residue of 1500 cub. centims. 
The apparatus was therefore altered to that shown in fig. 4, so as to make it possible 
to withdraw all the gas out of the gas-holder A. 
The left-hand exit led to the SPRENGEL’s pump; the compartment (a) of the 
drying-tube B was filled with soda-lime, and (b) with phosphoric anhydride. C isa 
2D2 
