Intelligence and Miscellaneous Articles- 477 



■a 



which last was determined by means of chloride of barium, and added 

 to that of the sulphur previously obtained ; by subtracting the weight 

 of the sulphur from that of the sulphuret of arsenic, the difference 

 gave the weight of the arsenic, which by calculation indicated that of 

 the arsenic acid contained in the mineral. , {TV fqni -»ht mo 



The water was separately determined by heating the mineral pre- 

 viously dried in vacuo in a platina crucible ; the loss of weight deter- 

 mining that of the water. 



Four analyses gave the following as the constituents of the mine- 

 rals from the places named : — 1. Scorodite in small greenish crystals 

 from Vaulry ; 2. scorodite in bluish crystals from Cornwall; 3. 

 bluish scorodite, on the surface of altered arsenical pyrites from Sax- 

 ony ; 4. neoctese in bluish transparent crystals from Brazil, 

 orfjjlo nor jj # III. S/JI ^iy. 



Arsenic acid ... . 5095 51-06 52-16 50-96 



- il{ Peroxide of iron.. 31-89 32'74 33-00 33-20 



Water 15-64 15-68 15-58 15-70 



98^48 g^is foo-Ti WM 



It appears therefore that both these minerals consist of -^fljjit 

 One equivalent of arsenic acid .. 58-00 50*00 



One ... peroxide of iron 40-00 34*48 



Two ... water 18-QO 15-52 



Equivalent ,yi Jvd .116* 100' 



M. Boussingault found that an arseniate of iron, occurring as an 

 earthy mass at Marmato, province of Popayan, yielded the following 

 substances :•— 



afajs \a& "Arsenic acid . $Vi\ , A W&ifp&X"'"**'* 01 »«a«toq 

 Peroxide of iron ! . ; .' 34'3 



Oxide of lead 00-4 



Water 16-9 



"fOl-2 01 * *° 9 ^ x0 ox ** 

 The composition of this substance agrees therefore perfectly with 

 that of scorodite ; the following are the results of Berzelius's analysis 

 of neoctese, which agree very nearly with all those above given, and 

 evince the propriety of M. Damour's suggestion, that the name of 

 neoctese should be abandoned and that of scorodite only retained : — 



Arsenic acid 50-78 



Peroxide of iron 34-85 



Water 1555 



Arseniate of alumina - 67 



Phosphoric acid and oxide of copper . . traces 



101-85 

 Ann. de Ch. et de Phys., Avril 1844. 

 



COMPARATIVE ANALYSIS OF ANATASE AND RUT1LE. 

 BY M. D AMOUR. 



The author observes, that it is well known that anatase crystallizes 

 in acute octahedrons, and that it cleaves parallel to the faces ; it 





