864 Prof. J. Joly on the 



The rammelsbergite examined showed no trace of sublimate 

 till raised to somewhat above 500°. This substance is de- 

 scribed as essentially NiAs 2 . An analysis on the apophoro- 

 meter gave the following percentages As, 58; (Ni, Co), 38. 

 A little sulphur was present which does not enter into the 

 weights found. The residue was mainly nickel. Now the 

 molecule Ni 3 As 4 would absorb the arsenic and nearly all the 

 (Ni, Co). A little cobalt sulphide would account for the 

 balance of the residue. I think it reasonable to assume that 

 the mineral in group III. is constituted in this manner. The 

 assumed molecule is similar to that of leucopyrite, which 

 also appears in this group. 



Another mineral within group III. was analysed in 

 order to account for its position : the chloanthite of the Val 

 d'Annivier (17). Chloanthite is essentially a diarsenide. This 

 specimen showed a very small sublimate (S 2 ) in group I. at 

 a temperature of 135°; which would represent a little loosely 

 combined arsenic if my assumptions are correct. This sub- 

 limate ceased to come off after a rise of some 30 degrees. 

 Between 220° and 270° a second sublimate (S 2 ) is obtained ; 

 small, but larger than the first. There is then an interval of 

 about 180 degrees over which no trace of sublimate appears 

 even on. prolonged observation. At 455° the evolution of As 

 recommences (S 3 ) and continues up to about 700° when there 

 is deflagration. After this but little arsenic remains. This 

 is given off at a temperature approaching 1000°. A little S 

 is probably present. Taking 16*7 mgrms. of the powdered 

 mineral, Sj+ S 2 amounted to 1*4 mgrms. ; S 3 to 13'4 mgrms., 

 and this includes the small final sublimate of As 2 ;] . The 

 residue weighed 7'2 mgrms. We have from these quantities 

 1 mgrm. of As in Sj + S 2 and 10' 1 mgrm. As in S 3 ; and as the 

 residue appeared to be almost entirely the oxide of nickel, we 

 get 5*7 mgrms. of Ni. The added weights are 16*8 mgrms. 

 The quantities afford as the relative numbers of atoms for 

 S!+S 2 , 4 As; for 8„ 40 As; for the residue, 30 Ni. Of 

 these atoms the molecule 10 (Ni 3 As 4 ) would leave only 4 As 

 as entering into the low temperature sublimates. This arsenic 

 may exist in the form 2 (As 2 S 3 ). The complete formula would 

 be As 2 S 3 , 5Ni 3 As 4 . It is worth comparing with this result 

 two analyses of chloanthite cited by Dana (loc. at.) Nos. 14 

 and 15, approximating to As, 58*7; (Ni, Co), 39 (mainly Ni); 

 S, 2*8. It will be found that these chloanthites are very closely 

 represented by the formula 3 Ni 2 S 3 , 20 (Ni, Co) 3 As 4 . 



Although the results given above seem in every case to 

 show that the molecule II As 2 is not necessarily present in the 

 substance subliming in the higher group, there is but little 



