CHEMISTRY. 389 



lent, aud oue iu which it is divalent ; since, however, we may pass from 

 cuprous to cupriccoiupouuds we are able to alter the electrical charge 

 ou the atom, increasing it by some simple multiple. He remarks fur- 

 ther that in the case of the two copper chlorides their heat of forma- 

 tion per chlorine atom is not very different. It is well known that the 

 heat of formation of a salt approximates to the heat of formation as 

 calculated from the electro-motive force developed when that salt is 

 formed in a voltaic cell ; hence from the heat of formation of the cuprous 

 or cnpric chloride, an approximate calculation can be made of the 

 difference of electric potential between the copper atom aud the chlo- 

 rine atom iu the two salts. But since the heat of formation per chlo- 

 rine atom is nearly the same, the difference of iiotential is nearly the 

 same in both salts; whence it follows that in doubling the electric 

 charge ou the copper atom the potential is not also doubled. This sig- 

 nifies, then, that the capacity of the atom for electricity is increased at 

 the same time. Laurie then suggests that the idea of atomic weight 

 may perhaps be replaced by the idea of charges of electricity ; that the 

 atoms of the elements are of the same weight and probably of the same 

 "stuff"," and that onl}^ two things condition the properties of the atom, 

 namely, its electrical charge and its electrical potential. If this be ac- 

 cepted Mendelejeff's table becomes a statement of the jjeriodic relation- 

 ship between these. (Nature, xxxv, 131.) 



Water of Crystallization^ by W. W. J. Nicol. — When a hydrated salt 

 is dissolved does it retain its water of crystallization or does this latter 

 cease to be distinguishable from the solvent water? Both views have 

 been held by chemists, but the author shows that the science of thermo- 

 chemistry clearly demonstrates that water of crystallization can not be 

 attached to the salt in solution. The argument will be found in the 

 original note. (Chem. News, liv, 53.) 



A Laic of Solubility, by William Ackroyd. — The author announces as 

 a new law of solubility the followiug: "A body will dissolve in a sol- 

 vent to which it is allied more readily than iu one to which it is highly 

 dissimilar." Thus organic bodies, generally speaking, require organic 

 solvents, inorganic bodies inorganic solvents. Exceptions to the law 

 are admitted by the author. (Chem. News, liv, 58.) 



Chemical Affinity and Solution. — In a paper before the Royal Society 

 of Edinburgh, presented in 1878, W. Durham stated his opinion, based 

 on the results of many experiments, that chemical combination, solu- 

 tion, and suspension of solids, such as clay, in water, differ in degree 

 only, and are manifestations of the same force; that there seems to be ' 

 a regular gradation of chemical attraction from that exhibited in the 

 suspension of clay in water up to that exhibited in the attraction of 

 sulphuric acid for water, whi(;h we call chemical affiuity. 



More recently Mr. E. Durham endeavored to show that the theory of 



