1 32 On the Liquefaction of Gases . [ 1 82-K 



50 Fahr. is equal to about forty atmospheres *, he must have 

 been mistaken. The following is his account : *' I now pro- 

 ceeded to the muriatic acid gas, and upon the condensation of 

 a small quantity of it, a beautiful 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 sub- 

 stance, which does not evaporate, but is instantly absorbed by 

 a few drops of water ; it is of a highly pungent 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 con- 

 densed without danger. My method of collecting 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 stopcock with the extremity of the retort." 

 xiii. 235. It seems probable that the facility of condensation, 

 and even combination, possessed by muriatic acid gas in con- 

 tact with oil of turpentine, may belong to it under a little 

 pressure, in contact with common oil, and thus have occasioned 

 the results Mr. Northmore describes. 



{Sulphurous Acid Gas. With regard to this gas, Mr. North- 

 more says, " Having collected about a pint and a half of sul- 

 phurous acid gas, I proceeded to condense it in the three cubic 

 inch receiver ; but after a very few pumps the forcing piston 

 became immoveable, being completely choked by the operation 

 of the gas. A sufficient quantity had, however, been com- 

 pressed to form vapour, and a thick slimy fluid, of a dark 

 yellow colour, began to trickle down the sides of the receiver, 

 which immediately evaporated with the most suffocating odour 

 upon the removal of the pressure." xiii. 236. This experi- 

 ment, Mr. Northmore remarks, corroborates the assertion of 

 Monge and Clouet, that by cold and pressure they had con- 

 densed this gas. The fluid above described was evidently 

 contaminated with oil, but from its evaporation on removing 

 the pressure, and from the now ascertained low pressure of the 

 vapour of sulphurous acid, there can be no hesitation in ad- 

 mitting that it was sulphurous acid liquefied. 



The results obtained by Mr. Northmore, with chlorine gas 

 and sulphurous acid gas, are referred to by Nicholson in his 

 * Philosophical Transactions, 1823, p, 198 or page 95. 



