444 Intelligence and Miscellaneous Articles. 



It thus appears from these researches that : — 



1. Any solid which clissolvea in a volatile liquid diminishes the 

 vapour-tension of this liquid, 



2. In all volatile solvents the molecular diminution of the 

 vapour-tension due to different compounds in solution approaches 

 two mean values, which vary with the nature of the solvent, and 

 one of which, called the normal, is twice that of the other : it is 

 that which is most frequently produced. 



As determined from a large number of solvents, values are given 

 for this constant Avhich amount to 0-0104. 



Hence it may he said that even 1 molecule of a solid dissolved in 

 100 molecules of any volatile solvent diminish the vapoior -tension of 

 the liquid hy an almost constant fraction of its value, and near to 

 0-0104. 



The formula /-/' ^ 0-0104 



may be utilized to determine the molecular weight of solid or vola- 

 tile bodies. If P is the weight of a substance dissolved in 100 

 grammes of a volatile liquid, M' the molecular weight of the 

 solvent, and M that of the body dissolved, we ha\e 



N = ?^, from which J^ = 0-0104 x ^,. 

 M M' /-/ 



It is thus possible to calculate M when M' is known, and con- 

 versely. 



This method of determiniug molecular weights is more difficult 

 to carry out, and is less exact than the cryoscopic method, which 

 depends on the freezing-point of solutions ; but it may be of great 

 service in many cases. — Journal de Physique, [2] vol. viii. p. 1. 



ON CHEMICAL ACTION BETWEEN BODIES IN THE SOLID STATE, 

 BY W. SPRING. 



The author mixed copper filings with perfectly dry pulverulent 

 mercuric cjiloride, and kept the mixture in closed glass tubes 

 which he shook from time to time. A very slow decomposition of 

 the two bodies set in, with the formation of cuprous and mer- 

 curous chlorides. In like manner there was a decomposition of 

 dry potassic nitrate with powdered sodic acetate freed from water 

 of crystallization ; for, after standing for four months in the drying- 

 vessel, the mass was deliquescent in the air, from which the 

 presence of potassic acetate may be inferred, since the original 

 salts are not deliquescent. This reaction takes place much more 

 rapidly at a high temperature ; for although the melting-point of 

 the two salts is above 300°, the mixture in question fused in a 

 water-bath in three hours to a white mass, which was also seen to 

 be deliquescent in air, — Bull, de VAcad. Boy. de Beige, vol, xvi, 

 p. 43, 18S8; Beihldtter der Physilc, vol. xiii. p, 123, 



