Cadmium, and Mercury. 

 Table XII. 



393 





Size of 



Refractive 







Method of preparation 



particles 



mm 



index 



Color 



Remarks 



Sodium thiosulpbate 







Nearly 



The purest 



in closed tube 



•004 and less 



2-38 



pure 

 orange 



orange 

 examined 



Do 



•001 — -003 



2-32 



Orange 



Globules 

 aggregated 



H 2 Scold._ 



•0005 





Orange- 

 yellow 



Clustered 



H,S and hot 5fo HC1 

 H 2 S and hot 28 % 



•004 





Orange 









H,SO, 



•008 





Deep 

 orange 



Aggregated 



Boiled several hours 







with sodium thio- 











sulphate. 



•007 — -ooi 



2'28± 



Bright 

 orange 





H 2 S in the cold 



•0005 — -001 

 •001 





Yellow 

 Yellow 





Na g S, closed tube 



2-40 





Commercial powder 











heated dry at 500° 



•0006 







Yellow 





Commercial powder 











Sample 1 



Compact 

 aggregate 



2-38 — 2-39 



Dull 

 orange 





Sample 2 



Do 



2-31 



Do 





and have no distinct faces. They are commonly aggregated 

 into stellate groups. In color they are not distinguishable from 

 cinnabar, and like cinnabar are optically uniaxial and positive, 

 but their refractive indices are lower and double refraction not 

 so strong. a> of several lots of crystals was determined for 

 wave-length about 650 pp. Monochromatic light could not be 

 used advantageously on account of weak illumination and dif- 

 fraction, but for the mean wave-length of the narrow band of 

 the spectrum transmitted by the sulphur-selenium mixture in 

 which the crystals were imbedded, the value of co was found to 

 be 2 - 60 to 2 - 61, the larger value being for the purest crystals. 

 The dispersion of the crystals is not accurately known, but it 

 appears to be about equal to that of the sulphur-selenium mix- 

 tures used Therefore, for Li-light &> = about 2-58 ; e-to = - 24 

 ± ' 03 according to several determinations on prisms of meas- 

 ured thickness. 



The third modification, a', is probably identical with the 

 mineral metacinnabar, but positive identification is not pos- 

 sible on account of the minute size and poor development of 

 the artificial crystals, and on account of the meager and conflict- 



