1819.] Muriatic Acid Gas. a3 
capacity of 25 cubic inches, was connected with ajar, contain- 
ig muriatic acid gasin 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 caoutchouc to a stop-cock 
at the top of the jar, its longer leg passing ito the tubulature of 
the retort, so as to terminate within an iach of its bottom, and 
the jomings 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 commence- 
ment of the experiment, the metallic filmgs, previously dry and 
warm, having been put into the retort, the atmospheric air is 
expelled by a moderate heat, and small portions of the muriatic 
acid gas are admitted until the retort is filled with the pure gas. 
The stop-cock is then closed, and heat is applied by a lamp to 
the bottom of the retort under a considerable pressure of mercury ; 
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 stop-cock being closed when the heat 
is applied, the hydrogen gas produced is expelled with any 
muriatic acid gas not acted on. 
In the principal experiment I employed, zinc filings were used 
in preference to iron, from the consideration that muriate of zine 
is less volatile than muriate of iron, and, therefore, would admit 
of a higher heat being applied to expel any water. One hundred 
grains of clean and dry zinc filings were introduced while warm 
into the retort; the air was expelled, and muriatic acid gas was 
admitted from the jar. On applying heat to the zinc, the retort, 
which was before perfectly dry, was bedimmed with moisture at 
its curvature, and small spherules collected at the top of the neck. 
These increased in size, and extended further as the experiment 
advanced. After a certain time, part of this disappeared in the 
interval of cooling, being absorbed by the deliquescent product ; 
but when the heat was again applied, it was renewed, and this 
in increased quantity, until at length, at the end of four days, 
during which heat had been frequently applied, the whole tube 
of the retort, seven inches in length, was studded with small 
globules of fluid. When the heat had been raised high, a beau- 
tiful arborescent crystallization appeared in a thin film on the 
body of the retort, but no part of this reached the neck. The 
retort was now detached ; the gas it contained was withdrawn 
by a caoutchouc bottle; a small receiver was adapted; and a 
slight heat having been applied to expel a little of the air, the 
joining was made close by cement. The receiver was surrounded 
with a freezing mixture, and heat was applied by a choffer to the 
Vou, XIII. N°. C 
