Dr. Henry’s Experiments on Ammonia , &c. 431 
purpose, the only metallic surface, exposed to the gas, con- 
sists of the sections of two platina wires, each —— of an inch in 
diameter, the wires themselves being inclosed in glass tubes 
which are sealed hermetically round them, and then ground 
away, so as to expose only the points. Nor does any dif- 
ference in the nature of the products arise from electrifying 
the gas either under increased or diminished pressure, the 
latter of which, it appeared to me probable, from the known 
influence of elasticity in impeding the combination of gaseous 
bases, might prevent the oxygen of the alkali from uniting 
with hydrogen to form water, and occasion the expansion of 
both into the state of gas. 
Having failed, therefore, to acquire, in this way, proof of 
the existence of oxygen in the volatile alkali, I was next led to 
seek for some unequivocal mode of evincing the production 
of water by the same operation ; a fact, which would be scarce- 
ly less satisfactory in establishing oxygen to be one of its 
constituents, than the actual separation of oxygen gas. The 
most careful observation of ammonia, during and after the 
agency of electricity, does not discover the smallest percep- 
tible quantity of moisture. In order, therefore, to subject the 
gas to a satisfactory test, I had recoure to the following con- 
trivance. Ammoniacal gas, I had previously found, may be 
so far desiccated by exposure to caustic potash, as to shew no 
traces of condensed moisture, on the inner surface of a thin 
glass vessel containing it, when exposed to a cold of o° Fah- 
renheit ; though the recent gas, by the same treatment, is 
made to deposit water in the state of a thin film of ice. A 
glass globe, of the capacity of between two and three cubical 
inches, was filled with gaseous ammonia, which was the» 
$K 2 
