240 Intelligence and Miscellaneous Articles. 



glory of the Society ; and the question remains, Is the Society now 

 so constituted that it represents the true state of astronomy in 

 England, and is the administration of its affairs such as to en- 

 courage, stimulate, and reward the patient worker in the humbler 

 ranks of observers, and the veteran who has won his laurels which 

 would gather lustre by the award of the Medal ? 



ON THE DETERMINATION OF THE BOILING-POINT OF LIQUEFIED 

 SULPHUROUS ACID. BY M. IS. PIERRE. 



In his very interesting memoir on sulphurous and chlorhydric 

 acids {Comptes Renclus, Jan. 13, 1873), M. Melsens says that from 

 1860 he has been seeking to determine the exact boiling-point of 

 liquefied sulphurous acid, that he has made very numerous trials 

 with vessels of all sorts, but that all his attempts have been fruit- 

 less. Nevertheless, if content with an approximation to o, 15 or 

 0°\2, it is very easy to determine the boiling-point of liquid anhy-: 

 drous sulphurous acid by following the process which I pointed 

 out twenty-six years since {Annates de Chimie et cle Physique, ser. 3, 

 vol. xxi.), in a memoir on sulphurous acid. This consists in pour- 

 ing into a tube of thin glass, 2*5 to 3 centims. in diameter, having 

 the form of a test-tube for gases, a certain quantity of sulphurous 

 acid previously cooled— fitting to the aperture a cork pierced with 

 two holes, one to give passage to the thermometer, the other 

 larger, intended to give free passage to the vapour of the acid by 

 means of a rather wide tube of thin glass — and, lastly, suspending 

 the apparatus in the air. This is what then takes place : — The 

 surrounding temperature being above that at which sulphurous 

 acid boils, the latter is very soon in ebullition ; but the heat ren- 

 dered latent by its vaporization lowers the temperature of the re- 

 maining liquid, and produces an abatement of the ebullition. This 

 is soon followed by a renewal; and thus a series of abatements and 

 renewals of ebullition is observed, during which the differences of 

 temperature indicated by the thermometer rarely reach 0°'2. 



The limits are still more contracted when the deposition of mois- 

 ture on the tube is avoided by covering with flannel the part con- 

 taining the liquid. With from 25 to 30 grammes of liquid, if the 

 operation takes place under favourable conditions, the experiment 

 may often last more than an hour. I have constantly repeated it 

 in my lectures for the last twenty-five years, on account of its 

 facility. 



I have thus found a number which differs very little from 8° 

 below zero (Centigrade). The process, extremely simple, is appli- 

 cable to all liquefied gases which can be kept in an open -vessel, — 

 that is to say, which in a certain time emit by ebullition a quantity 

 of vapour that absorbs and renders latent an amount of heat equal 

 to that received by the liquid from the surrounding medium— a 

 condition from which results a temperature of spontaneous ebulli- 

 tion sensiblv constant.— Comptes Renclus deVAcademie des Sciences, 

 Jan. 27, 1873. . .- 



