32 Dr. Murray’s Experiments on [JAN. 
This accumulated in globules, and at length ran into a small 
portion in the bottom; the sides were bedewed for a length of 
six inches, and a thin film of moisture appeared beyond nearly 
its whole length. f 
By the muriatic acid gas being extricated in the preceding 
experiment from nearly dry materials, and by its previous trans- 
mission over an extensive surface of lodse muriate of lime, it was 
inferred that it would be free from hygrometric vapour ; and that 
it held no moisture, was apparent from no trace of it appearing 
in the anterior portion of the tube. To obviate, however, 
entirely, any supposed fallacy from this source, the experiment 
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 ajar with a stop-cock adapted to it. This- 
was connected by a short tube with a caoutchouc 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 quick- 
‘silver trough, and fresh quantities, which had been equally with 
the other exposed to muriate of lime, were added, as was neces- 
sary. Water almost immediately appeared in the tube beyond 
the iron filings; it collected in spherules, and continued to 
accumulate as the gas continued to be transmitted for a length 
of about seven inches. A portion of the gas, which escaped 
from the extremity, was clouded, and deposited a film of 
moisture on the sides of the jar in which it was received over 
quicksilver. The quantity of gas transmitted amounted to about 
35 cubic inches. 
There are some difficulties in conducting the experiment in 
the manner now described, from the consolidation of the metallic 
matter, and the volatilization of the product. It was also of 
some importance to vary the experiment. I, therefore, performed 
it in another mode. Metals scarcely act on muriatic acid gas 
at natural temperatures, but from such a degree of heat as could 
be applied by a small lamp, beth iron and zinc were acted on; 
the gas suffered diminution of volume, hydrogen was formed, 
and a sensible production of moisture took place. The simplest 
mode of exhibiting this is ‘to introduce iron or zinc filmgs, pre- 
viously dry and warm, into a retort fitted with a stop-cock, 
exhausting it ; then admitting dry muriatic acid gas, and apply- 
ing heat by a small lamp to the filings in the under part of the 
body of the retort. Moisture soon appears at its curvature in 
small globules, and increases on successive applications of the 
heat with the admission of the requisite quantities of gas. 
To conduct the experiment, however, on a larger scale, | 
employed a different apparatus. A tubulated retort, of the 
