Royal Society. 235 



tained in the form of hydrate, exhibits a brisk incandescence 

 when exposed to a temperature of dull redness, and its physical 

 properties are found to be greatly modified. Denoting these 

 two conditions of the earth by Zr (a) and Zr (b), it is easy to 

 suppose that their mixture in varying proportions will produce 

 numerous variations in the physical characters of the compound 

 of which this substance forms part. 



The author gives, finally, a list of the densities of a number of 

 zircons. 



Lemoine* has found that when sulphur is combined with red 

 phosphorus in excess, a new sulphide of phosphorus, P 2 S 3 , is 

 obtained. When 1 equivalent of sulphur is mixed with 1 of 

 red phosphorus and the mixture heated to 100°, a violent action 

 is set up accompanied by great evolution of heat. The residue 

 consists of sesquisulphide of phosphorus mixed with excess of 

 hposphorus. The two bodies are most readily separated by 

 solution in bisulphide of carbon. Whatever excess of red phos- 

 phorus is taken, the substance formed is the same ; but if the 

 sulphur is in excess, tersulphide of phosphorus is obtained. 



Sesquisulphide of phosphorus crystallizes from sulphide of 

 carbon or from chloride of phosphorus in right rhomboidal 

 prisms. 



It melts at 142°, and distils between 300° and 400°. At 260° 

 it volatilizes completely in a current of dry carbonic acid. The 

 sublimate thus obtained does not colour polarized light, which 

 circumstance, together with its aspect and the mode of its group- 

 ing, place it in the regular system. It is therefore dimorphous. 

 It is almost unalterable in the air and in cold water. 



XXVII. Proceedings of Learned Societies. 



ROYAL SOCIETY. 



[Continued from p. 159.] 



June 16, 1864. — Major-General Sabine, President, in the Chair. 



THE following communication was read : — 

 " Description of a New Mercurial Gasometer and Air-pump." 

 By T. R. Robinson, D.D., LL.D., F.R.S., &c. 



In some experiments on the electric spectra of metal and gases, 

 I felt the want of a mercurial gasometer for working with such of 

 the latter as are absorbable by water. That of Pepys is on too large 

 a scale for my requirements, and it seemed better to contrive one 

 more easily manageable, which I saw could also be made to act as a 

 mercurial air-pump. In this I have succeeded to my satisfaction ; 

 and I hope that a description of it may be useful to those who are 

 engaged in similar researches. 



* Comptes Rendus, May 16, 1864. 

 R2 



