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XXX. 2 he Chromojenetic Properties of Sulphur and certain 

 other Elements. By Oliver C. M. Davis, D.Sc, and 

 Frederic William Bixon, Ph.D.* 



IN a critical examination of coloured inorganic binary 

 compounds it is interesting to notice that a considerable 

 number of these bodies contain the element sulphur. The 

 nature of these sulphur compounds has given rise to much 

 speculation and research over prolonged periods. During 

 more recent years the study of organic chemistry has enabled 

 vast numbers of sulphur-containing coloured compounds to 

 be prepared and examined. 



Much work has been done on the relationship between the 

 properties of elementary substances and the compounds 

 derived from them, so that a brief reference to the colour of 

 elementary sulphur will not be out of place here. 



As is well known, the commonest variety of this element, 

 is yellow in colour, but, according to Engelf, there is an 

 orange-coloured variety ; Orloff: % also considers that he has 

 prepared a blue variety of sulphur. In all probability the 

 different colours observed in the case of free sulphur are not 

 brought about by the same cause, and may be due to the 

 size of the particles or to variations in intramolecular 

 structure. These variations in the colour of elementary 

 sulphur are of special interest when we remember that the 

 substitution of sulphur for oxygen in certain molecules may 

 give rise to yellow, orange, blue, and other colours, the 

 corresponding oxy-compounds being colourless. This pro- 

 duction of colour has been so frequently observed that the 

 group — C : S has been referred to as a chromophore group 

 (Ludwig Gattermann §). An interesting observation made 

 by Hewitt || with reference to the striking difference between 

 the C : and : S group contains the statement : '" The 

 attraction between carbon and sulphur is less than that 

 between carbon and oxygen." Purvis IT suggests that un- 

 saturated valencies of elements may influence light-absorption, 

 and points out that the valency of sulphur in the : S group 

 is not completely saturated, and the attraction between 

 carbon and sulphur is thereby less than between carbon and 



* Communicated bv the Authors. 



t Engel, Compt. Rendu*. 1901. 



X Orloff, J. Huss. Phys. Chem. 1901. 



§ Gattermann, Berichte, 189o. 



|| Hewitt, Int. Congress of Applied Chem. 1909. 



IT Purvis, Chem. Soc. Trans. 1914. 



