196 Experiments on Muriatic Acid Gas, 
composition of nitrogen than the existence of water as a consti- 
tuent of muriatic acid. No weight, I believe, is due to such an 
assumption; but if any importance were attached to it, it is pre- 
eluded if water is obtained from the action of metals on muriatic 
acid gas. ’ 
I have executed the experiment in several forms; and in all 
with a more or less satisfactory result. 
One hundred grains of iron filings, clean and dry, were strewed 
for a length of five or six inches, in a glass tube which was placed 
in an iron case, across a small furnace, so as to admit of being 
raised toa red heat. This tube, of about two feet in length, 
was connected with a wide tube eight inches long, containing 
dry and warm muriate of lime ; and this was further connected, 
at its other extremity, with a retort affording muriatic acid gas, 
from a mixture of supersulphate cf potash and muriate of soda. 
The open extremity of the long tube, dipped by a slight curva- 
ture in quicksilver. On the iron being raised to ignition, and 
the transmission of the acid gas being conducted slowly, elastic 
fluid escaped from the extremity of the tube, which was found 
to be hydrogen; and though no trace of moisture appeared in the 
anterior part of the tube, it immediately condensed in that part 
which was cold, beyond the izon filings. This accumulated in glo- 
bules, and at length ran into a small portion in the bottom; the 
sidés were bedewed for a length of six inches, and a thin film of 
moisture appeared beyoud, nearly its whole length. 
By the muriatie acid gas being extricated in the preceding 
experiment from nearly dry materials, and by its previous trans- 
mission over an extensive surface of loose muriate of lime, it was 
inferred, that it would be free from hygrometrie vapour; and 
that it held no moisture, was apparent from no trace of it ap- 
pearing in the anterior portion of the tube. To obviate, how- 
ever, entirely, any supposed fallacy from this source, the experi- 
ment was performed in the following manner. One hundred’ 
grains of clean and perfectly dry iron filings were put into a long 
glass tube, which was placed, as before, across a small furnace. 
Muriatic acid gas had been kept in contact with dry muriate of 
lime for three days, in a jar with a stopcock adapted to it. This 
was connected, by a short tube with a caontchouc collar, with 
the tube containing the iron filings and a little of the muriatic 
acid gas being passed through the tube to expel the air, the tem- 
perature was raised to ignition. The slow transmission of the gas 
was continued by the pressure of the mercury in the quicksilver 
trough, and fresh quantities, which had been equally with the 
other exposed to muriate of lime, were added, as was necessary. 
Water almost immediately appeared in the tube beyond the iron 
filings, it collected in spherules, and continued to accumulate : 
: the. 
