298 EXPERIMENTS AND OBSERVATIONS 
‘There are some difficulties in conducting the experiment in 
the manner now described, from the consolidation of the me- 
tallic 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 muria- 
tic 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, hydro- 
gen was formed, and a sensible production of moisture took 
place. The simplest mode of exhibiting this, is to introduce 
iron or zinc filings, previously dry, and warm, into a retort 
fitted with a stop-cock ; exhausting it ; then admitting dry mu- 
riatic acid gas ; and applying 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, I em- 
ployed a different apparatus. A tubulated retort, of the capaci- 
ty of twenty-five cubic inches, was connected with a jar, con- 
taining 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 shorter leg with a collar of caoutchoue 
to a stop-cock at the top of the jar, its longer leg passing into 
the tubulature of the retort, so as to terminate within an 
inch of its bottom, 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 posi- 
tion of the retort, may be placed beside the other, on the shelf 
of the trough. At the commencement 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 
