282 ON THE DELiaUESCENCE OF BODIES. 



13. That sulphuric acid is not decomposed in its action on 

 starch and sugar of milk : and that^ from the facts mentioned, 

 it is much more probable, that the acid takes from these sub- 

 stances oxigen and hidrogen in the proportions necessary to 

 form water. 



VII. 



Abstract of a Paper on the Deliquescence of Bodies j ly Mr. 

 Gay-Lussac*. 



Deliquescence (f\^ the 17th of May [1812] I communicated to the So- 



reducible to ^J/ ciety of Arcueil some observations on the property that 

 general pnn- , j- 1 ^ r r / 



ciples. bodies iaave of attracting the moisture of the air, and which is 



more particularly designated in chemistry by the name of 

 deliquescence. This property, hitherto badly analysed, may 

 be reduced to general principles, by which we may easily 

 ascertain what bodies possess it, the variations it undergoes ac- 

 cording to the temperature, and the degree of the hygrometer 

 at which it begins to manifest itself. 

 Owing to the As the deliquescence of a body is owing to its affinity for 

 a"ubstan"c e for ^^^^^' ^"^ ^^ ^^^ ^^^^^ of this affinity is to diminish to a cer- 

 water. tain degree the elastic force of the vapour contained in a deter- 



minate volume of air, it is very essential, both for knowing 

 Mode of ascer- whether deliquescence can take place, and for obtaining com- 

 tajnmg it. parable results, to place each body in an atmosphere completely 

 saturated with moisture. Thus we find, that muriate of soda. 

 Exists where it sugar, &c., are very deliquescent ; and that even nitre, and 

 su^speaed.^^^ many other substances, in which this property had not been ob- 

 served, possess it more or less. 

 Temperature We cannot thus ascertain the degree in which a substance 

 to be a^ttended jg deliquescent : but, to accomplish this, we must first observe, 

 that, the deliquescence of a substance depending on its affinity 

 for water, and this affinity itself being strikingly modified by 

 heat, it is necessary to consider each temperature in par- 

 ticular. 

 Method of Suppose then a given substance, solid or liquid ; and we 



ii.j I e e- ^jgj^ j^ know its degree of deliquescence in an air saturated 



* Ann. de Chim. toI. LXXXII,p. 171. . 



-> with 



