300 Apparatus for Solidifying Carbonic Acid. 



A cast-steel plug with stop-cock precisely similar to the one de- 

 scribed, screws into the receiver, as the other does into the gene- 

 rator. The tube L screws into the plug which is inserted in the 

 receiver, and the other end, turned to a conical point, fits accu- 

 rately into a cavity in the plug B, and is held in its place by 

 means of the stirrup screw M. Another stirrup screw N, and 

 block of wood O, secures the receiver C in its place. 



To use this apparatus the generator and receiver are separated, 

 and the plug B being removed, two pounds of bicarbonate of soda, 

 made into a paste with the same weight of water, are introduced 

 into A, and twenty ounces* of strong sulphuric acid are poured 

 into several lead vessels, made by soldering bottoms in pieces of 

 lead tube a little shorter than the length internally of the gene- 

 rator, and of such a diameter that they will just pass the aperture. 

 These being nearly filled with acid are dropped into the genera- 

 tor, which, after the plug B is inserted, is allowed to lie on one 

 side for fifteen or twenty minutes, or a less time if it is several 

 times rolled over to mix the acid with the soda. The receiver is 

 then attached to it as seen in the figure, by means of the stirrup 

 screws M and N ; and if kept sufficiently cool by means of ice, 

 the liquid carbonic acid formed in A will shortly be distilled over 

 into C, the passage between them being of course previously 

 opened by means of the stop-cocks before described. 



The stop-cocks are now to be closed and the receiver, which 

 now contains the liquid carbonic acid, separated from the genera- 

 tor. _ A small tin cup is then to be attached to the tube L, pre- 

 cisely as in Dr. Mitchell's apparatus,! ^o receive the jet of acid 

 from the receiver. It is essential that the liquid acid should escape 

 into this cup, which is effected by having a small tube pass from 

 the steel plug nearly to the bottom of the receiver, or by invert- 

 ing the receiver before opening the stop-cock. 



The best method of testing the strength of the apparatus, is by 

 means of a hydraulic press, but it can be done as effectually by 

 permitting it to lie, when charged, exposed to the direct rays of 

 the sun, and excluded from currents of air, till the temperature 



* The quantity of acid required to saturate or neutralize the soda would be a 

 little more than 24 oz., or 22 oz. only if the soda is in crystals, but something less 

 than this should always be used. 



t Journal of the Franklin Institute, Vol. xxii, p. 289, and Vol. xxxv, p. 346, of 

 this Journal. 



