A NEW CONSTITUENT OF THE ATMOSPHERE. 197 
about 30 grams, absorbs between seven and eight litres of nitrogen. It is essential 
that oxygen be excluded from the tube, otherwise a fusible substance is produced, 
possibly nitrate, which blocks the tube. With the precaution of excluding oxygen, 
the nitride is loose and porous, and can easily be removed from the tube with a rod ; 
but it is not possible to use a tube twice, for the glass is generally softened and 
deformed. 
(g.) Nitride of aluminium has been investigated by Mauuer.* He obtained it in 
erystals by heating the metal to whiteness in a carbon crucible. But aluminium 
shows no tendency to unite with nitrogen at a red heat, and cannot be used as an 
absorbent for the gas, 
(h.) GERRESHEIM? states that he has induced combination between nitrogen and 
mercury; but the affinity between these elements is of the slightest, for the 
compound is explosive. 
(z.) In addition to these, metallic manganese in a finely divided state has been 
shown to absorb nitrogen at a not very elevated temperature, forming a nitride of the 
formula Mn-N,.t 
(j.) [A mixture of nitrogen with hydrogen, standing over acid, is absorbed at a 
fair rate under the influence of electric sparks. But with an apparatus such as 
that shown in fig. 1, the efficiency is but a fraction (perhaps 4) of that obtainable 
when oxygen is substituted for hydrogen and alkali for acid.—April, 1895. | 
4, Early Experiments on sparking Nitrogen with Oxygen in presence of Alkali. 
Tn our earliest attempts to isolate the suspected gas by the method of CAVENDISH, 
we used a RunMKoRFF coil of medium size actuated by a battery of five Grove cells. 
The gases were contained in a test-tube A, fig. 1, standing over a large quantity of 
weak alkali B, and the current was conveyed in wires insulated by U-shaped glass 
tubes CC passing through the liquid round the mouth of the test tube. The inner 
platinum ends DD of the wires were sealed into the glass insulating tubes, but 
reliance was not placed upon these sealings. In order to secure tightness in spite 
of cracks, mercury was placed in the bends. This disposition of the electrodes 
complicates the apparatus somewhat and entails the use of a large depth of liquid in 
order to render possible the withdrawal of the tubes, but it has the great advantage 
of dispensing with sealing electrodes of platinum into the principal vessel, which 
might give way and cause the loss of the experiment at the most inconvenient 
moment. With the given battery and coil a somewhat short spark, or arc, of about 
5 millims. was found to be more favourable than a longer one. When the mixed 
gases were in the right proportion, the rate of absorption was about 30 cub. centims. 
* © Journ. Chem. Soc.,’ 1876, vol. 2, p. 349. 
+ ‘Annalen der Chemie u. Pharmacie,’ 195, 373. 
¢ O: Preatineer, ‘Monatsh. f. Chemie,’ 15, 391. 
