M. C. Deville on the origin of Granite. 177 



Slow cooling, or to speak more generally, a slow and gradual 

 mode of formation, allows the molecules to become associated 

 under circumstances in which each takes with it the normal 

 quantity of heat ; from this a stable equilibrium results, at any 

 rate under the actual conditions of temperature. In the case of 

 sulphur, for example, octahedral or normal sulphur is formed of 

 2*07 spec, grav., which is quite stable at ordinary temperatures ; 

 while the two others, soft or vitreous sulphur and insoluble 

 sulphur, become more or less transformed into octahedral sulphur, 

 either spontaneously or by simple actions of contact. 



It must also be added that the fourth condition, prismatic 

 sulphur, whether prepared by fusion, or crystallized from a 

 hot solution of ether, alcohol, chloroform, or benzole, &c, cor- 

 responds to a condition in which the molecules, although 

 possessing more heat than the normal quantity, maintain their 

 equilibrium a certain time, and are then rapidly changed below 

 a certain temperature. But the curious part of this is, that this 

 temperature is not constant, but varies with the nature of the 

 solvent, and probably also with other circumstances; so that 

 this phenomenon of transformation does not appear to be con- 

 nected with a fixed temperature which the substance obtains on 

 cooling, but rather with the quantity of heat which the liquid had 

 assimilated and had abandoned at a certain moment. Lastly, 

 it may be concluded from my experiments*, that when sulphur 

 is heated in an open vessel, it appears to pass successively through 

 different conditions of equilibrium ; sometimes it strongly retains 

 heat, at others it rapidly parts with it : this seems to constitute 

 a sort of rotation, of which the prismatic condition, which com- 

 mences at about 109 degrees, is only the first term. 



Among the very interesting researches which many chemists 

 have lately undertaken on the properties of insoluble sulphur, 

 that of M. Cloez has greatly struck me. Some years after I had 

 described the sulphur made insoluble by tempering, MM. Fordos 

 and Gelis announced that they had obtained an analogous and 

 probably identical sulphur by the action of water on sulphide of 

 nitrogen or chloride of sulphur, &c. M. Cloez, by varying the 

 conditions of the experiment, has produced indifferently soluble 

 or insoluble sulphur ; and he adds f, " It is thus shown that 

 chloride and bromide of sulphur produce insoluble sulphur by a 

 rapid decomposition, and soluble sulphur by slow decomposition," 

 — an evident confirmation of what I had previously announced. 



I have also been struck with M. Debray's curious experiment J, 

 in which he reproduces at will prismatic sulphur in bisulphide 



* Ann. de Chim. et de Phys. 3 ser. vol. xlvii. p. 110. 

 t Comptes Rendus, vol. xlvi. p. 496. 

 X Ibid. vol. xlvi. p. 576. 



