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 zinc 

 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 

 vshelf of the mercurial trough, by a tube bent twice at right 

 angles, and fitted by its shorter \e^ with a collar of caoutchouc 

 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 



