290 Notice of some Recent 



researches of Mr. Graham have clearly proved that there 

 is no such law in nature as isomerism, and that the term 

 should be dropped, unless we choose to designate every 

 new fact by a Greek compound. There is an amusing dis- 

 cussion in the January number of the Journal de Pharmacie, 

 between Couerbe and Pelletier, in which the absurdity of 

 the doctrine is exposed. The former asserts, that C H is 

 not isomeric, with C 2 H 2 , while the latter affirms, that 

 it is so, and laughs at the contrary idea. The truth is, 

 they may both be merry. There seems little doubt, that 

 the different forms of the arsenious acid depend upon the 

 relations of that substance to water. 



The same phenomenon of the disengagement of light had 

 been observed before, during the crystallization of sulphate 

 of potash. Rose supposes that the salt was obtained from 

 the residue after the distillation of nitric acid, and was, 

 therefore, sesqui-sulphate of potash, which dissolves in that 

 state in water ; but, when it separates from its solution, is 

 converted according to Phillips into bi-sulphate and sul- 

 phate of potash.* 



Specific heat of salts soluble in water. — Rudberg has fur- 

 nished a formula for determining this important question. 

 Let M represent the water in which a salt is dissolved, 

 T its temperature, m, t, c respectively the mass, tempera- 

 ture and specific heat of the salt, that of the water taken as 

 unity, t the temperature of the liquid after solution, and X 

 the quantity of heat thereby absorbed or evolved. The last 

 \is a general term compounded of 1, the heat become latent 

 by the solution of the salt ; 2, the heat disengaged by the 

 change of volume ; and 3, of the heat produced by chemical 

 combination, when the salt undergoes such a combination. 

 Without considering how the one or the other of these 

 Greek letters can be determined by itself, it is remarked, 

 that their sutn, positive or negative, is, in the first place, a 

 necessary proportional of the mass of salt ; and, secondly, 

 is unchangeable, while the proportion of the salt to the 

 water is not changed. When two experiments are made 

 with this proportion constant, but the temperature of the salt 

 different, the temperature of the water besides in both trials 

 being either equal or not, we have in the first case, 



* Poggendorff's Annalen, xxxv. 481. 



