At constant 

 pressure 



Chase.] ^^^ [April 21, 



Observers. 

 At constant f Andrews, 

 volume \ V. Than, 



J. Thomsen, 

 Favre and Silbermann, 

 ( Schuller and Wartha, 



The observations were made respectively in 1848, 1881, 1873, 1852 and 

 1877. The corresponding molecular heats, as given hy Naumann (see 

 Note 16) for three of the above observers, differ slis;htly from 2 x the 

 above values of 0, the greatest difference being | of one per cent. The 

 mean values, if we allow equal Aveight to the present note and toXote 16, 

 after making the proper correction in the observations at constant volume, 

 are p = 92,739,500 ; m = 331,280. This value of p differs by less than 

 ^Jj of one per cent, from the mean of the combined results in Note 15 

 (92,737,100). , 



231. Molecular Volume of Solids. 



E.Wilson (^Proc. Roy. Soc, xxxii, 457-91) discusses the relations of 

 molecular volume to chemical constitution, furnishing new evidence of 

 harmonic oscillation. He states the three following propositions, and 

 thinks that his tables lend comparatively greater support to the third, 

 while the first and second must, for the present, be considered more 

 hypothetical : 



(i.) When any number of similar ^iom?. combine, the volume of the 

 resulting molecule is equal to that of the uncombined atom. 



(ii.) When dissimilar atoms combine, the volume assignable to each 

 atom is some simple submultiple or aliquot part of its atomic volume, and 

 the resultant molecular volume is the sum of those volumes. 



(iii.) Every element in its various compounds is capable of assuming 

 different volumes bearing a simple proportion to one another, such as 

 1:2, 1:3, 2:3, &c. 



He also adduces evidence in support of Kopp's conjecture that elements 

 may undergo different degrees of condensation in different radicles of the 

 same compougd, and he shows the agreement of his results with those 

 which were obtained hy Loschmidt from gaseous interdiffusion. 



232. Variability of Crystalline Angles. 



F. Pfaff {Jour. Chem. Soc, June, 1881, Abstr. p. 356) has made a series 

 of measurements, from which he concludes that the limits of admissible 

 correction of measured angles by calculation from rational axial sections 

 must be carried further than has hitherto been the case. W. H. Perkin 

 {lb. Aug., 1881, 409-453), in discussing the isomeric acids obtained from 

 coumarin and the ethers of hydride of salicyl, gives seven sets of crystal- 

 line measurements, with forty-ninecomparisonsof calculated and observed 

 angles. Taking the range between the limits of observation, which are 

 given in twenty -six of the comparisons, or the deviations of the observed 



