the Unit-Steve Theory. 325 



Valency has also been shown (Le Bas, Proc. Chem. Soc. 

 xxiii. p. 134) to be an energy property by means o£ the 

 molecular heats of combustion of the normal paraffins. (See 

 also Chem. News, xlv. p. 247, xcvi. p. 58.) 



These results are intrinsically interesting, and, i£ accepted, 

 would no doubt be of the highest importance. 



The writer proposes, in this and succeeding papers, to 

 subject the molecular volumes o£ the members o£ a number 

 o£ organic series under corresponding conditions to a critical 

 examination, in order to show the generality of the above 

 relation. 



The idea that the volumes of the atoms in compounds are 

 simply related is not new, for it was considered by Schroder 

 so far back as 1877 (Ber. x. pp. 848, 1871 & foil.). 



Traube has shown, from a consideration of molecular 

 solution volumes, that there is a connexion between volume 

 and valency (Ber. 1894, xxvii. pp. 3171-3179). 



Following the suggestion of Barlow and Pope, the above 

 author has recently demonstrated the fact that the molecular 

 refractions of compounds belonging to many series are pro- 

 portional to the atomic refraction of combined hydrogen 

 (Ber. 1907, xl. (1) pp. 130-139). Traube has also applied 

 the above principle to his theory of molecular volumes (Ber. 

 1907, xl. (3) pp. 723-733, 734-736 & foil.; Annalen, 1907, 

 xxii. pp. 518-542). 



Recently Barlow and Pope have developed the view that 

 crystalline form and molecular structure can be correlated 

 (Trans. Chem. Soc. 1906, lxxxix. p. 1675). 



Their theory is based upon two fundamental concepts : 



(1) That the volumes of crystalline solids are simple additive 

 functions of the- fundamental valencies of the compounds. 



(2) That these solids may be supposed to consist of structural 

 units in tactile arrangement and built up from the spheres 

 of influence of their component atoms. 



In 1905 the author developed the present theory, sub- 

 stantially as it is now being presented, but was prevented by 

 circumstances from publishing it at that time. 



The molecular volumes of many compounds were shown 

 to be integral multiples of that of combined hydrogen when 

 examined under corresponding conditions, so that there is a 

 proportionality between volume and valency. 



Views regarding the compact structure of liquids and 

 solids similar to those of Barlow and Pope were at that time 

 entertained. At the present time it is proposed simply to 

 investigate the valency relation, and to show that the laws of 

 correspondence and additivity are very closely connected. 



