with Observations on its Chemical Constitution. 197 
the gas continued to be tr ansmitted 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 oi the 
jar in which it was received over quicksilver. The quantity of 
gas transmitted amounted to about thirty-five cubic inches, 
There are some difficulties in conducting the experiment in 
the manner now described, from the consol’dation of the metal- 
lic 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, both iron and zine 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 zine filings, pre- 
viously dry, and warm, into a retort fitted with a stopcock ; ex- 
hausting 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 
sinall 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, I em- 
ployed a different apparatus. A tubulated retort, of the capacity 
of twenty-five cubie inches, was connected with a jar, containing . 
muriatic acid gas in contact with muriate of lime, on the shelf of 
the mercurial trough, by a tube bent twice at right angles, and 
fitted by its Sumior leg with a collar of caoutchouc to a stop- 
cock at the top of the jar, its longer leg passing into the tubu- 
lature of the retort, so as to terminate within an inch of its bot- 
tom, and the joinings being rendered air-tight. The retort is 
so placed, that heat can be applied by a lamp to the bottom, 
and its neck dips, by a short curved tube, under a jar filled with 
quicksilver, which, by the reverted position of the retort, may be 
placed beside the other, on the shelf of the trough. At the com- 
mencement of the experiment, the metallic filings, previously dry 
and warm, having been put into the retort, the atmospheric air is. 
expelled by a moderate heat, and sinall portions of the muriatic 
acid gas are admitted, until the retort is filled with the pure gas. 
The stopcock is then closed, and heat is applied by a lamp to 
the bottom of the retort, under a considerable pressure of mer- 
cury; any small portion ‘of gas, expelled at the extremity, being 
received in the small jar. The heat can thus be successively, 
cautiously applied, and this, as the experiment proceeds, to a, 
greater extent, in consequence of the diminution of volume that 
takes place. Fresh quantities of muriatic acid gas are admitted 
from time to time from the jar; and the stopcock being closed 
N3 when 
