600 
sensitive to light was not at all affected. With the 
same exceptions, the effect was obtained only after 
partial drying, but appeared to be destroyed by 
complete calcination. Some of the substances did 
not always respond, even when taken from the same 
bottles as portions that did. None were chemically 
pure. 
It seems possible that the phenomenon is due to 
chemical reactions with the active nitrogen, or it may 
be due to the presence of free electrons. An insulated 
electrode was sealed into the exhaust tube about a 
metre from the discharge tube and connected with an 
electroscope. When the latter was negatively charged 
little effect was produced by a stream of active 
nitrogen just past the stage of luminosity. When 
it was positively charged, it was rapidly discharged. 
When an uncondensed discharge was used with the 
same nitrogen, or the condensed discharge through 
inactive nitrogen, little effect was produced in either 
case. Recombination was apparently complete before 
the gas reached the electrode. As there must have 
been equal numbers of positive and negative ions, 
the loss of the positive charge must have been due to 
the greater mobility of the negative ions, and presum- 
ably they were free electrons. An attempt to measure 
the specific ionic velocities of the ions failed, on account 
of the electrostatic disturbances due to the disruptive 
discharge. 
Under the conditions of these experiments, the line 
spectrum of nitrogen was not given by the light in 
the discharge tube. This indicates that molecular 
dissociation was small. The ions were probably for 
the most part molecular ions and electrons. The 
isolated bands in the first group which are the most 
characteristic feature of the spectrum of the active 
nitrogen afterglow must, of course, be due to molecular 
radiators. The afterglow depends upon the presence 
of a trace of oxygen (or some electronegative element) 
and is destroyed by the presence of more than a trace. 
It may be that in pure nitrogen there is no appreciable 
afterglow, because the great electron density favours 
rapid recombination. When there is an excess of 
oxygen, the electrons may all attach themselves to 
oxygen, and the final step may be the formation of 
nitric oxide, with the emission of Deslandres’ third 
group of bands. If there is enough oxygen to remove 
most but not all of the electrons, recombination may 
go on slowly, the afterglow continuing while it lasts, 
the’ spectrum being due to the recombination of 
electrons with positive molecular ions. Of course 
the alternative is not excluded that active nitrogen 
may be monatomic and the characteristic radiation 
is emitted when it resumes its ordinary state. 
E. P. LEwiIs. 
Department of Physics, 
University of California. 

Active Hydrogen by the Action of an Acid 
on a Metal. 
EvipENcE for the formation of active hydrogen 
from its positive ion in an acid has been negative. 
The reports of the latest workers in this field, Wendt 
and Landauer (Jour. Amer. Chem. Soc. 42, 930: 1920) 
show that there are certain difficulties to be met. 
The main one is to eliminate the moisture that 
accompanies a rapid evolution of hydrogen and at 
the same time not to destroy the active hydrogen if any 
were formed. If the velocity of the gas stream were 
too low, the active component would decay before 
reaching the sulphur. Then if the velocity were too 
high the moisture carried over would form a protecting 
film on the powdered sulphur and prevent the re- 
action between the two to form hydrogen sulphide. 
NO. 2792, VOL. IIT] 
NATURE 

[May 5, 1923 
During the work on the activation of hydrogen by 
corona discharge it was found by Wendt and Grubb 
(Jour. Amer. Chem. Soc. 42, 937: 1920) that active 
hydrogen combines with pure nitrogen togive ammonia. 
This method of testing for active hydrogen can be 
used to good advantage where moisture is carried 
along with the evolved hydrogen, since the spray 
does not prevent the contact of active hydrogen and 
the nitrogen. 
If hydrochloric acid or sulphuric acid is dropped 
upon metallic magnesium suspended in such a way 
that the metal is at no time immersed or partly 
covered with any large portion of liquid, the dro 
of acid can react with the metal in the shortest possible 
time. This gives off hydrogen very rapidly, in fact 
almost explosively, and with a minimum quantity of 
spray. If this evolved hydrogen is brought in contact 
with pure nitrogen it is found that ammonia is formed 
very readily. The active hydrogen was then passed 
through a plug of glass wool before coming in contact 
with the pure nitrogen. The activity of the hydrogen 
still persisted as shown by the formation of ammonia. 
Therefore, the activity of the hydrogen cannot be 
due to ions or atomic gas. But Langmuir (Jour. 
Amer. Chem. Soc. 34, 1324 (1912)) has shown that 
monatomic hydrogen does not react with nitrogen to 
form ammonia. In view of this fact, if we allow pure 
nitrogen to escape at the surface of the magnesium 
where the hydrogen is evolved we find a maximum 
quantity of ammonia formed. The amount of 
' ammonia formed increases with an increase in the 
rate at which the acid is dropped upon the metal. 
This, of course, means that the amount of the active 
component varies with the velocity of the gas stream. 
If the acid is dropped on the metal very slowly 
and the evolved hydrogen passed through glass wool 
before coming in contact with nitrogen, no ammonia is 
formed. This indicates that the active hydrogen has 
reverted to the ordinary form before meeting the stream 
of nitrogen. The life of the active gas seems to be 
not longer than two minutes. This checks very 
closely with the life of triatomic hydrogen formed by 
other methods. 
These results seem to substantiate the theory of 
Wendt and Landauer (Jour. Amer. Chem. Soc. 44, 
510: 1922), namely, that triatomic hydrogen ought 
to be produced wherever atomic hydrogen is evolved. 
It is reasonable then to expect that a higher percentage 
of active hydrogen would be found in the gas evolved 
from the surface of the metal, than in the molecular 
hydrogen subject to electronic bombardment in a 
discharge tube. In the former all the hydrogen 
evolved goes through the atomic state, while in the 
latter case only a very small amount of atomic gas 
may exist at one time. The discharge would also 
destroy some of the active variety. 
The preliminary results to determine the percentage 
of activation are in harmony with this theory. Further 
work is in progress to determine the quantitative 
relations of some of the factors involved. 
A. C. GRUBB. 
Department of Chemistry, 
University of Saskatchewan, 
Saskatoon, Sask., Canada, April 2. 

The Viscosity of Liquids. 
I wisH very briefly to supplement the remarks made 
in.a previous communication on this subject in which 
I have suggested that the viscosity of liquids and its 
variation with temperature may be explained on the 
hypothesis that the liquid state of aggregation is 
composite in character; that is, is composed in part 

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