1824] On, the Liquefaction of Gases. 129 



Sulphurous Acid Gas. It is said that sulphurous acid gas 

 has been condensed into a fluid by Monge and Clouet, but I 

 have not been able to find the description of their process. 

 It is referred to by Thomson, in his * System,' first edition, ii. 

 24, and in subsequent editions ; by Henry, in his ( Elements/ 

 i. 341 ; by Accum, in his ' Chemistry,' i. 319 ; by Aikin, * Che- 

 mical Dictionary,' ii. 391 ; by Nicholson, c Chemical Dictionary,' 

 article GAS (sulphurous acid) ; and by Murray, in his * System/ 

 ii. 405. All these authors mention the simultaneous application 

 of cold and'pressure, but Thomson alone refers to any authority, 

 and that is Fourcroy, ii. 74. 



It is curious that Fourcroy does not, however, mention con- 

 densation as one of the means employed by Monge and Clouet, 

 but merely says the gas is capable of liquefaction at 28 of 

 cold. " This latter property," he adds, " discovered by citizens 

 Monge and Clouet, and by which it is distinguished from all the 

 other gases, appears to be owing to the water which it holds in 

 solution, and to which it adheres so strongly as to prevent an 

 accurate estimate of the proportions of its radical and acidifying 

 principles." 



Notwithstanding Fourcroy's objection, there can be but little 

 reason to doubt that Monge and Clouet did actually condense 

 the gas, for I have since found that from the small elastic force 

 of its vapour at common temperatures (being equal to that of 

 about two atmospheres only*), a comparatively moderate dimi- 

 nution of temperature is sufficient to retain it fluid at common 

 pressure, or a moderate additional pressure to retain it so at 

 common temperature ; so that whether these philosophers ap- 

 plied cold only, as Fourcroy mentions, or cold and pressure, as 

 stated by the other chemists, they would succeed in obtaining 

 it in the liquid form. 



Chlorine. M. de Morveau, whilst engaged on the application 

 of the means best adapted to destroy putrid effluvia and con- 

 tagious miasmata, was led to the introduction of chlorine as the 

 one most excellent for this purpose ; and he proposed the use 

 of phials, containing the requisite materials, as sources of the 

 substance. One described in his 'Traite des Moyens de 

 clesinfecter 1'air ' (1801), was of the capacity of two cubical 

 inches nearly ; about 62 grains of black oxide of manganese in 

 * Philosophical Transactions, 1823, p. 191 or page 90. 



K 



