ON MURIATIC ACID GAS, &C. «j 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 ( a,t 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 muri- 

 ate of zinc is less volatile than muriate of iron, and therefore 

 would admit of a higher heat being applied to expel any wa- 

 ter. One hundred grains of clean and dry zinc filings were in- 

 troduced, 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 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 

 mow detached j the gas it contained was withdrawn by a caout- 



P p 2 chouc 



