182 Prof. Magnus on Red and Black Sulphur, 



which had been uninterruptedly exposed to heat for eight hours 

 gave a yellow solution ; and the insoluble part, 15*04 per cent., 

 was pure yeQow in colour. 



To prove that for the formation of black sulphur, not repeated 

 heating, but sudden cooling is necessary, the following experi- 

 ment was instituted. A quantity of common sulphur was heated 

 to 300° C. in a glass vessel with a narrow neck, which was closed 

 by a cork and placed in a very large sand-bath, where it was 

 completely surrounded by sand. After the sulphur had com- 

 pletely attained the above temperature it was allowed to remain 

 in the large quantity of sand and cool down slowly to the tem- 

 perature of the room. This operation was repeated ten times 

 with the same sulphur. After this treatment the sulphur gave 

 a colourless solution with bisulphide of carbon ; the insoluble 

 residue amounted only to 1-4 per cent, of its weight, but had all 

 the properties of black sulphur. This small quantity of black 

 sulphur was evidently caused by some parts cooling too quickly. 



It follows from this, that black sulphur is formed only by 

 sudden cooling. 



In the well-known brown, tough, or so-called 7-sulphur, I 

 found that some black sulphur was also present, although it had 

 only been once fused : and probably the brown colour and tough- 

 ness of this sulphur is closely connected with the amount of 

 black sulphur it contains. Black sulphur, like yellow, becomes 

 electric by friction. I must reserve the determination of its 

 specific gravity for another opportunity. 



Red Sulphur. 



It has been already remarked that black sulphur, when tem- 

 pered, i. e. when retained for some time at the temperature of 

 130° C, dissolves easily in bisulphide of carbon, and gives a deep 

 red solution. When this solution is evaporated, it behaves in 

 exactly the same manner as before described in the case of re- 

 melted sulphur; that is to say, it gives a red solution, from 

 which yellow octahedral crystals separate, and a red mother- 

 liquor remains behind, which also permeates, more or less, the 

 yellow crystals. If care be taken to prevent the too quick eva- 

 poration of the bisulphide of carbon, by placing the solution 

 under a bell-glass whose rim does not close perfectly, and to 

 take away the crystals which are formed during this slow evapo- 

 ration as soon as ever a small quantity of the same is visible, 

 then the crystals will appear more and more red in colour ; the 

 mother-liquor, however, will at last become thick and tough. 

 If left in this condition it hardens gradually, and finally forms a 

 solid red mass. 



