Mr. Faraday on the Liquefaction of Gases. 237 



ceivers, containing from three and a half to five cubic inches, and 

 a quarter of an inch thick ; and occasionally a syphon gauge. 

 Sometimes as many as eighteen atmospheres were supposed to 

 have been compressed into the vessel, but it is added, that the 

 quantity cannot be depended on, as the tendency to escape even 

 by the side of the piston, rendered its confinement very difficult. 



Now that we know the, pressure of the vapour of chlorine, 

 there can be no doubt that the following passage describes a true 

 liquefaction of that gas. " Upon the compression of nearly two 

 pints of oxygenated muriatic acid gas in a receiver, two and a 

 quarter cubic inches capacity, it speedily became converted into a 

 yellow fluid, of such extreme volatility, under the common pres- 

 sure of the atmosphere, that it instantly evaporated upon opening 

 the screw of the receiver ; I need not add, that this fluid, so highly 

 concentrated, is of a most insupportable pungency." " There was 

 a trifling residue of a yellowish substance left after the evaporation, 

 which probably arose from a small portion of the oil and grease 

 used in the machine," fyc. xiii. 235. 



Muriatic Acid. — Operating upon muriatic acid, Mr. Northmore 

 obtained such results as induced him to state he could liquify it 

 in any quantity, but as the pressure of its vapour at 50° F. is 

 equal to about 40 atmospheres*, he must have been mistaken. The 

 following is his account: " 1 now proceeded to the muriatic acid 

 gas, and upon the condensation of a small quantity of it, a beau- 

 tiful green-coloured substance adhered to the side of the receiver, 

 which had all the qualities of muriatic acid ; but upon a large 

 quantity, four pints, being condensed, the result was a yellowish 

 green glutinous substance, which does not evaporate, but is in- 

 stantly absorbed by a few drops of water ; it is of a highly pun- 

 gent quality, being the essence of muriatic acid. As this gas 

 easily becomes fluid, there is little or no elasticity, so that any 

 quantity may be condensed without danger. My method of col- 

 lecting this and other gases, which are absorbable by water, is 

 by means of an exhausted Florence flask, (and in some cases an 

 empty bladder) connected by a stop cock with the extremity of 

 the retort." xiii. 2.J5. It seems probable that the facility of con- 

 • Philosophical Transactions, 1883j p. 198. 



