ae MELA 
ON MURIATIC-ACID Gas, &e. 299 
and'small portions of the muriatic acid gas are admitted, until the 
retort is filled with the pure gas. The stop-cock is then clo- 
sed, 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 alae zine filings were 
used i in preference to iron, from the. consideration, that muri- 
ate of zinc is less volatile than muriate of iron, and therefore 
sl admit of a- higher heat being applied to expel any wa- 
- One hundred grains of clean and dry,zine filings were in- 
el an 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 farther 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 beautiful arborescent 
crystallization appeared in a thin film on the body of the’re- 
tort, but no part of ‘this reached the neck. The retort was 
now. detached ; the gas it contained was withdrawn by a caout- 
Pp2 chouc 
