ISO Prof. Magnus on Red and Black Sulphur. 



as a moistened porcelain plate, in very thin layers, it is, wlieil 

 cool, quite black, soft and viscous, and capable of being drawn 

 out into long thin threads. It retains its viscidity for many 

 hours, and often days. It then becomes solid, and has a glassy 

 fracture, without any trace of crystalline structure. 



As it is not possible to cool the whole mass suddenly, portions 

 of it always assume a dark brown instead of a black colour ; and 

 when the sulphur is preserved for some time, the black parts 

 remain unchanged, whilst the colour of the brown becomes 

 somewhat clearer, and thus gives a lighter tint to the whole 

 mass. By again heating the so-changed mass to 300° C. and 

 suddenly cooling it, it again appears black ; but it now changes 

 more easily than before, inasmuch as it contains more yellow 

 sulphur, the latter being foraied at every fusion of black sulphur. 

 The more the black sulphur contains of yellow, the more readily 

 its colour changes. 



Pure black sulphur is insoluble in bisulphide of carbon, 

 scarcely soluble in alcohol, aether, benzole, and oil of turpentine, 

 but more soluble in chloroform. It fuses at nearly the same 

 temperature as common sulphur. At 180° to 200° C. it becomes 

 a thick liquid. It can be boiled without changing its colour. 

 When distilled it gives common yellow sulphur. As black sul- 

 phur, however, is obtained by separating the yellow from the 

 repeatedly melted sulphur, it contains the whole of the impuri- 

 ties, insoluble in bisulphide of carbon, which were present in the 

 quantity of common sulphur that was employed in its preparation; 

 and as a great quantity of common sulphur must be used in 

 order to obtain a small quantity of black, these impurities, which 

 in sublimation remain behind, form a considerable part of the 

 black sulphur. Nevertheless, from red sulphur also we can obtain 

 black which contains no such impurities (see p. 185). When 

 the latter is sublimated, a scarcely ponderable residue remains, 

 which arises from a little dust. For, in the many operations to 

 which red sulphur must be subjected, it is scarcely possible to 

 protect it completely from dust. 



If black sulphur be heated only to 140° or 160°, and retained 

 some time at this temperature, it does not become soft when 

 suddenly cooled, but hardens quickly to a crystalline dark brown 

 mass which dissolves very easily in bisulphide of carbon, and 

 gives a deep red solution. This brown mass may be called tem^ 

 pered sulphur. In the production of black sulphur some of this 

 is always present, because, in pouring out the mass heated to 

 300° C, part of it unavoidably sinks to a lower temperature 

 before it can reach the cold water. 



From the whole deportment of black sulphur, and particularly 

 from the fact, that when heated to a proper temperature it be- 



