Prof, Magnus on the Allotropic Conditions of Sulphur, 527 



external layer was dissolved, dried them in porous paper, and 

 without touching them with the fingers, introduced them into 

 the hot sulphur which had been purified by two distillations. 

 Even this coloured the sulphur. 



The colour which is imparted to sulphur by sugar, starch, 

 cotton, &c., is indeed more brown than red, but its solution in 

 bisulphide of carbon shows always the pure red colour. 



From this it is clear, that other than fatty substances colour 

 sulphur, and the red colour of sulphur cannot serve as an 

 evidence of the presence of a fat. It appears that very various 

 substances so decompose at a higher temperature, that a certain 

 constituent of them unites with the sulphur and forms with it 

 the strongly colouring body. I have, however, not yet been 

 able to ejQPect its separation from the excess of sulphur. 



The colouring property of this compound is so great, that not 

 only sulphur which has been touched by the hands is coloured red 

 by the fat which is thereby imparted to it, when heated to 300° C, 

 but also sulphur which has been several times heated to 300° C, 

 and each time poured out, assumes a reddish colour even when 

 it has not been touched by the hands. This probably arises 

 from small particles of dust which during the cooling settle 

 upon it from the air, and enter into the colouring compound at 

 each new melting. 



By these experiments I have been led to several facts con- 

 cerning the allotropic conditions of sulphur. In the establish- 

 ment of these I had the assistance of M. R. Weber, and to such 

 an extent, that the research may be considered as executed by us 

 in common. 



If common yellow sulphur be heated to 350° C, or to that 

 temperature at which, after it has been viscid, it becomes 

 fluid again, and if it be then allowed to cool slowly, it is, as is 

 well known, completely or almost completely soluble in bisulphide 

 of carbon. In order that it may be so, it is good to shake it 

 repeatedly during the cooling, for otherwise that portion on the 

 side of the vessel would cool too rapidly and thereby become 

 insoluble in bisulphide of carbon. 



For if sulphur, which has been heated to 300° C, be allowed 

 to cool too rapidly, it is no longer completely soluble in bisul- 

 phide of carbon, but leaves, according as the cooling has been 

 more or less rapid, a greater or lesser part undissolved. If the 

 cooling be effected in such a manner that the sulphur be poured 

 in a thin stream into cold water, the well-known white sulphur 

 is obtained. This leaves undissolved, as will be seen from the 

 following Table, from something over thirty to something over 

 forty per cent, of its weight *. 



* M. Ch. Saint-Claire Deville states in his treatise Des modifications du 



