CHEMISTRY. 



By George F. Barker, 

 Professor of Physics in the University of Pennsylvania, Philadelphia. 



CHEMICAL PHYSICS. 



Angus Smith has suggested a new series of elemental molecules, the 

 relative weights of which are produced by squaring the atomic weights 

 and dividing by the equivalence. This idea was reached in the course 

 of his investigations into the absorption of gases by charcoal, in wiiich 

 it appeared that the gases were absorbed in perfectly definite volumes. 

 Thus, eight volumes of oxygen are absorbed for one of hydrogen ; but as 

 the former is IG times as heavy, the weights absorbed are as IL'.S : 1. 

 But this is ^(16)2; i. c, half the square of the density, or half the square 

 of the atomic weight, or half tlie i)roduct of the two. Of nitrogen 4.G0 

 volumes are absorbed, or 14x'l.<>G by Aveight, G5.;>; this number is ^(l-t)^. 

 Of compound gases the law is different. Carbonous oxide is absorbed 

 to the extent of G volumes, carbon dioxide G+1G=L*2 volumes, marsh gas 

 G+4=: 10 volumes, nitrogen monoxide 8+4.G(»=12.GG volumes. Hence 

 the new molecular weight of CO2 is sinq)ly 22', »^'c. — [Xuture^ xix, 354, 

 February, 1879.) 



Thomsen has studied the relation between the total energy developed 

 in the chemical reactions which occur in various kinds of voltaic bat- 

 teries and the energy which appears in the form of current electricity. 

 He used a thermal method of measuring the total energy, and found that 

 the whole of the energy developed in the chemical change appeared as 

 electric energy in Daniell's battery on closed circuit, and also in the 

 other forms of battery in which the metallic surface of the negative elec- 

 trode is not changed by the electrolytic process. When nitric acid is 

 used as the electrolyte the same total conversion of energy takes place, 

 but the gradual absorption by the liquid of reduction products dimin- 

 ishes the result. — {Nature, xxiii, 207, December, 1880.) 



Hesehus has made a series of experiments upon the change in vol- 

 ume and elasticity undergone by palladium when it occludes hydrogen. 

 Wires 500"^™ long and 0.4"'"^ diameter were stretched in a tube of glass 

 placed vertically and filled with diluted sulphuric acid, and made the 

 cathode. By a cathetometer the elongation was directly measured 

 during the absorption. The pure palladium wire elongated S"""*, while 

 S. Mis. 31 19 2^^ 



