A NEW CONSTITUENT OF THE ATMOSPHERE. 195 
the air during the half hour which he continued working at a time varied in general 
from 40 to 120 measures, but was usually greatest when there was most air in the 
tube, provided the quantity was not so great as to prevent the spark from passing 
readily.” The “ measure ” spoken of represents the volume of one grain of quicksilver, 
or ‘0048 cub. centim., so that an absorption of one cub. centim. of mixed gas per hour 
was about the most favourable rate. Of the mixed gas about two-fifths would be 
nitrogen. 
3. Methods of Causing Free Nitrogen to Combine. 
The concord between the determinations of density of nitrogen obtained from 
sources other than the atmosphere, having made it at least probable that some heavier 
gas exists in the atmosphere, hitherto undetected, it became necessary to submit 
atmospheric nitrogen to examination, with a view of isolating, if possible, the unknown 
and overlooked constituent, or it might be constituents. 
Nitrogen, however, is an element which does not easily enter into direct combination 
with other elements ; but with certain elements, and under certain conditions, combi- 
nation may be induced. The elements which have been directly united to nitrogen 
are (a) boron, (b) silicon, (c) titanium, (d) lithium, (¢) strontium and barium, 
(f) magnesium, (g) aluminium, (h) mercury, (2) manganese, (j) hydrogen, and 
(k) oxygen, the last two by help of an electrical discharge. 
(a.) Nitride of boron was prepared by W6HLER and DeviLiE* by heating amorphous 
boron to a white heat in a current of nitrogen. Experiments were made to test 
whether the reaction would take place in a tube of difficultly fusible glass ; but it was 
found that the combination took place at a bright red heat to only a small extent, 
and that the boron, which had been prepared by heating powdered boron oxide with 
magnesium dust, was only superficially attacked. Boron is, therefore, not a convenient 
absorbent for nitrogen. [M. Moissan informs us that the reputation it possesses is 
due to the fact that early experiments were made with boron which had been 
obtained by means of sodium, and which probably contained a boride of that metal. 
—April, 1895. ] 
(b.) Nitride of silicont also requires for its formation a white heat, and complete 
union is difficult to bring about. Moreover, it is not easy to obtain large quantities 
of silicon. This method was therefore not attempted. 
(c.) Nitride of titanium is said to have been formed by DrviiLE and Caron,{ by 
heating titanium to whiteness in a current of nitrogen. This process was not tried 
by us. As titanium bas an unusual tendency to unite with nitrogen, it might, 
perhaps, be worth while to set the element free in presence of atmospheric nitrogen, 
with a view to the absorption of the nitrogen. This has, in effect, been already done 
* © Annales de Chimie,’ (3), 52, p. 82. 
+ Scuurzenpercur, ‘Comptes Rendus,’ 89, 644. 
£ ‘ Annalen der Chemie u. Pharmacie,’ 101, 360. 
DH Cnes 
