170 Sir H. Davy on the experiments in which water 
the glass became opaque, and gained a pearly lustre, and a 
combination of chlorine and lead sublimed from the hotter into 
the colder part of the tube. In the second, the surface of the 
tube became slightly opaque, but no sublimate was formed. 
When line clean iron wire was introduced into such tubes, 
and made red hot, and muriatic acid gas passed over it, no 
particular precautions being taken to free the tubes from com- 
mon air, much more water appeared ; but this excess of water 
principally owed its existence to the combination of hydro- 
gen disengaged from the muriatic acid gas by the iron 
with the oxygen of the common air. I say, principally , be- 
cause an inappreciable quantity must have been deposited from 
the vapour of hydrated muriatic acid in the muriatic acid 
gas. This was proved by filling the whole apparatus with 
hydrogen in another experiment, and generating the muriatic 
acid gas in a retort filled with hydrogen, when the water 
produced was no more than might have been expected from 
the action of the muriatic acid gas on the oxide of lead and 
alkali in the glass. I give the details. Above 21 grains of 
the first combination of chlorine and iron were formed ; the 
quantity of moisture collected by bibulous paper, and which 
was, a strong acid solution of the proto-muriate of iron, 
amounted to less than half a grain, and of this not more than 
two-thirds could have been water. Now, if chlorine had been 
decomposed in this operation, the quantity of water ought to 
, have been at least ten times as great. 
I have shown by numerous experiments, that in the action 
of muriatic acid gas upon metals, hydrogen, equal in bulk to 
half the volume of the gas, is produced ; it is therefore evi- 
dent, that if water had been generated by the action of m.u- 
