ALLOTROPISM BASED ON THE THEORY OF DIRECTIVE VALENCY. 321 



bouring atoms. What, however, happens when, as in the 

 case of an element, the atoms composing the molecules are 

 the same ? Is it possible that valency direction is affected 

 by the conditions under which the molecules are formed ? 

 The assumption that variation of the conditions attending 

 the formation of the molecule may alter the relative 

 direction of the "tubes of electric force," the directions 

 in which the electrons are discharged, will account for 

 variations in the structure of the resulting molecule which 

 may possibly have a bearing on the different physical forms 

 which the molecule is capable of assuming. 



In wiiat follows, the data concerning the molecular 

 weights and allotropic forms of the elements are taken for 

 the most part from Roscoe and Schorlemmer's "Treatise 

 on Chemistry," Vol. i, 1905. All other references quoted 

 have been verified. 



Sulphur. 

 The molecular weight of sulphur as determined by the 

 freezing point depression and boiling point elevation of 

 solutions in carbon-bisulphide and naphthalene, corresponds 

 to a molecule consisting of eight atoms. The vapour 

 density diminishes rapidly with increase of temperature* 

 until at 860° it corresponds with the formula S 2 , and remains 

 constant up to 1400°. At temperatures nearer the boiling 

 point of sulphur (400°) the vapour-density is nearly constant 

 at pressures between 540 mm. and 125 mm., and corres- 

 ponds to a formula between S 7 , and S 8 , the molecular weight 

 diminishing rapidly with reduced pressure at this temper- 

 ature. It appears most probable that the sulphur molecule 

 contains eight atoms at lower temperatures, splitting up 

 into S 2 molecules as the temperature rises (or at 440° with 

 diminishei pressure). 



With regard to its valency, sulphur is divalent in its 

 principal compounds with hydrogen and the metals, occas- 



T— Dec. 6, 1911. 



