178 Prof. Magnus on Red and Black Sulphur. 



The porous, insoluble sulphur which remains after the solu- 

 tion of the soluble part falls easily to a fine powder, which in the 

 water-bath coalesces to a solid mass. 



Flowers of sulphur also contain insoluble sulphur, inasmuch as 

 they are obtained by sudden cooling. But the greater part of them 

 is always soluble ; only about a third of their weight is insoluble. 



If the sudden cooling of sulphur be repeated, after heating it 

 each time to about 300° C, it has a darker colour after each 

 operation. After six, but often after ten, repeated fusions and 

 sudden coolings it becomes dark brown when cold, and crystal- 

 lizes, like common melted sulphur, in prisms. In this phase 

 C. Deville has called it red prismatic sulphur. I shall call it 

 repeatedly-melted, or shorter, remelted sulphur, in order to distin- 

 guish it from the red sulphur to be afterwards described. The 

 colour of remelted sulphur sometimes changes after a few hours, 

 but generally after some days, to a pale red ; at the same time 

 the crystals become opake, and in all probability assume the 

 octahedral form. If the sulphur is fused often enough, however, 

 e. g. twenty times, and each time, but particularly the last time, 

 well cooled, it continues amorphous a long time and retains the 

 red-brown colour. When common sulphur is lieated only to 

 160° or 170° C, it does not assume the red-brown colour, even 

 when it has been repeatedly fused at this temperature and well 

 cooled every time. At this temperature some insoluble yellow 

 sulphur is alone formed. In an experiment where the same 

 mass of sulphur was fused ten times at 1 60° to 170°, and quickly 

 cooled every time, the yellow colour was retained, but more 

 resembling that of amber. Afterwards it was soluble in bisul- 

 phide of carbon and colourless ; only 9 per cent, of its weight 

 was left behind as insoluble yellow sulphur. 



By remelted sulphur, in the following pages, is meant sulphur 

 which has been repeatedly fused at ^z^^ temperatures and quickly 

 cooled until it has assumed the red-brown colour. 



Such remelted sulphur differs from common in more respects 

 than colour, for in the liquid state at all temperatures, and hence 

 at the point of crystallization, it has a wine-red colour ; whereas 

 common sulphur assumes a clear, yellow colour, when by cool- 

 ing it passes from the thick to the thin liquid state, and it 

 retains this colour until it becomes solid. 



When bisulphide of carbon is poured over such remelted sul- 

 phur immediately after it is cool and still red-brown, or after it 

 nas lain some time and assumed the pale red colour, a red solu- 

 tion is obtained. Its colour will only be weak red or brownish, 

 if, after the last fusion, the sulphur has been suddenly cooled, 

 but deep red if it has been cooled slowly. This difference, which 

 does not appear to have been observed before, is caused by the 



