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XXV. On Red and Black Sulphur. By Professor G. Magnus*. 



ALTHOUGH the remarkable deportment of sulphur, when 

 exposed to high temperatures, has often been the subject 

 of highly interesting investigations, we are still far from a com- 

 plete knowledge of all its properties, inasmuch as the different 

 forms which sulphur can assume are more numerous than one 

 would expect. Accidentally I have been led to observe a few 

 allotropic modifications which I believe to be new. In order to 

 describe how these are obtained, it will be necessary to mention 

 several facts already made known to us by the researches of 

 Frankenheim, Marchand and Scheerer, Brame and C. St. Claire- 

 Deville. 



Insoluble Yellow Sulphur. 



If common sulphur be heated to a temperature of about 360° 

 C. and then suddenly cooled, it is no longer completely soluble 

 in bisulphide of carbon after becoming cool. Also, if sulphur 

 be heated to a lower temperature, and cooled quickly, it is only 

 partially soluble in bisulphide of carbon. The well-known tough, 

 brown sulphur, which Berzelius distinguishes by 7, is not com- 

 pletely soluble. When bisulphide of carbon is poured over this, 

 it immediately becomes white and opake in several places, and 

 gradually so throughout the entire mass. Whether this change 

 is caused by its becoming crystalline, or whether, after the solu- 

 tion of the soluble part, the insoluble remains behind in a porous 

 condition and thereby appears opake, I will not venture to decide. 



If common sulphur be allowed to cool slowly instead of quickly, 

 it is, with the exception of the foreign constituents which may 

 be present, completely soluble. 



Insoluble sulphur may be kept for weeks and months without 

 its becoming soluble. If melted, however, and allowed to cool 

 slowly, or retained at a temperature not exceeding 130° C, it 

 again becomes soluble. It also reacquires this solubility if heated 

 in a water-bath, but in this case a longer time is necessary. 



It is difficult to determine the lowest temperature to which 

 common sulphur must be raised in order to become insoluble by 

 being cooled quickly, because it becomes partially cool in the 

 neck of the vessel out of which it is poured, and because the 

 stratum in immediate contact with the cold water, or the cold 

 body on which it is poured, cools more quickly than the interior 

 mass. Probably this is also the reason why the whole quantity 

 of sulphur which is employed does not become insoluble ; for 

 even when a very thin thread of it is poured into cold water, 

 only about 40 per cent, of it is insoluble. 



* From Poggendorff 's Annalen, vol. xcii. p. 308. 

 Phil. Mag. S. 4. Vol. 8. No. 51. Sept. 1854. N 



