Prof. J. Joly on the Apophorometer . 305 



the experiment the latter element is abundantly present. 

 The silver appears as a brilliant frosting, the gold in fibres 

 and, perhaps, crystals. 



Bornite. Cu 3 Fe S 3 (variable). Weight 25*6 mgrms. 



At lowest red heat S0 2 emitted ; recognized by the odour. 

 Oily drops were formed on the glasses. [This liquid v\as 

 found to be a strong acid and is doubtless H 2 S0 4 , the 

 water being obtained mainly from the atmosphere.] The 

 residue fuses and gives off no further sublimate up to a 

 bright yellow heat. Loss of weight found to be only 

 2 mgrms. 



Bornite (as above). — The last result suggested a gain in 

 weight by the oxidation of the residue. To test this another 

 quantity (18'5 mgrms.) was roasted On a weighed ribbon in 

 free air. The result was an increase of weight by a fraction 

 of a milligram. This substance should be dealt with in the 

 absence of oxygen. 



Realgar. As 2 S 2 . — Although heated at a very carefully 

 graduated temperature, the substance did not appear to 

 decompose generally into S and As. There was some 

 liberation of S, however, the characteristic odour of S0 2 

 being detectable. As the heating continued the remarkable 

 effect was observed of a deposit of what was evidently 

 orpiment on the upper glass and of realgar on the lower. 

 Examination with the microscope showed that the minute 

 globules composing the realgar were in general considerably 

 larger than those composing the orpiment. There were also 

 beads of a black vitreous substance on the ribbon : probably 

 As. There has, therefore, been a loss of S and some 

 separation of As and a redistribution of the S so that the 

 trisulphide As 2 S 3 (orpiment) is formed along with the 

 realgar. The gravitational separation of the two sulphides 

 is remarkable. 



Embolite. Ag (CI, Br). — This melted to an oily brown 

 liquid which appeared to sublime bodily. The whole of 

 the sublimate was easily soluble in strong ammonia. The 

 platinum was left clean. 



Tetradymite. Bi 2 (Te, S) 3 . Bi 51*9 ; Te 48*1 ; S small in 

 amount or absent. Weight taken 27*1 mgrms. 



(1) Black-grey sublimate formed at a sub-luminous tem- 

 perature. It was allowed to collect for 10 minutes. Weight 

 2*3 mgrms. 



