368 SIR WILLIAM CKOOKES ON SCANDIUM. 



oppositely polarised. The red transmitted ray is extinguished when the short 

 diagonal of the nicol is parallel to the long axis of the crystal, and the reflected green 

 ray is extinguished when the long diagonal of the nicol is parallel to the long axis of 

 the crystal. Light passing along the axis of the crystal is crimson, and not polarised. 



[June 2nd, 1910. I have submitted the metallic green crystals of this salt to the 

 low temperature of liquid air with a view to ascertain what change of colour, if any > 

 accompanies the reduction of temperature. After an exposure for ten minutes in 

 liquid air the green colour becomes paler and more of a yellowish hue, while the 

 transmitted light changes from crimson to deep brown. On removing the platino- 

 cyanide from the liquid air the normal colours come back as the salt warms up to the 

 temperature of the laboratory.] 



The crystals are soluble in water, forming a colourless solution, and are insoluble 

 or nearly so in absolute alcohol. Boiled in alcohol they dehydrate, turning white 

 but not dissolving. The white dehydrated salt dissolves easily in water, and on 

 evaporation separates out in crystals of the normal appearance. 



Analysis. 



(1) 5755 gr. of well crystallised and air-dried scandium platinocyanide were 



dissolved in water and precipitated hot with ammonia. The scandia was 

 filtered off, well washed, dried, ignited, and weighed. It weighed 0'627 gr., 

 = 0'40G gr. of scandium. The filtrate was evaporated to dryness in 

 platinum, and the residual ammonium platinocyanide slowly decomposed by 

 heat and then ignited strongly. The platinum left from the decomposition 

 weighed 2 '446 gr. 



(2) 9-612 gr. of scandium platinocyanide were fused at a full red heat with potassium 



bisulphate. Hydrocyanic acid was evolved with much intumescence and 

 separation of platinum, and the mixture finally fused quietly to a clear liquid. 

 The mass was extracted with water containing a little acid, and the platinum 

 filtered off'; it weighed 4'028 gr. 



Ammonia in excess was added to the filtrate and the precipitated scandia 

 collected; it weighed M32 gr., = 0733 gr. of scandium. 



(3) 10741 gr. of air-dried scandium platinocyanide were kept over sulphuric acid 



in a desiccator for 80 hours. It lost 2 '121 giv of water. The salt was then 

 put into a hot-air oven and kept at 100 for 17 hours. It became a good 

 canary-yellow, and was found to have lost an additional 0'1343 gr. The 

 temperature was raised to 160 for 10 hours, when an additional 0'644 gr. of 

 water was driven off The temperature was finally raised to about 180, when 

 the salt began to decompose. Calculated out, these losses nearly approximate 

 to successive losses of 15, 1, and 4 molecules of water, with half a molecule 

 still remaining in the salt at 160, and only driven off as decomposition 

 commences. 



