Carbon loss, caustic-soluble

COMPARISON OF IGNITION LOSS, CAUSTIC-SOLUBLE CARBON CONTENT VOLUMETRIC REDUCTION RATIO... 

Raw fume may be washed with water to remove halides. To prevent loss of zinc and other metals into the wash solution it is usual to use sodium carbonate solution for fume washing. This converts soluble zinc and other metal chlorides and fluorides to sodium chloride or fluoride and insoluble metal carbonates which are retained with the fume. Wash solutions are generally maintained at a pH of 9.0 to 9.2. Alternatively the fume can be first washed with water and the resulting solution treated with sodium carbonate or caustic soda to precipitate zinc (Chabot and James, 2000). 

The dihydrate is formed by evaporation at ordinary temperature of an ethereal solution of the hexahydrate which has been dried with calcium nitrate or by crystallisation of the hexahydrate from concentrated nitric acid solution. It yields small lustrous plates, thick and square, probably rhombic, and possessing a green fluorescence. It melts at 179-3° C. It is much more stable than the trihydrate, and can be kept in a vacuum desiccator with caustic alkali or i hosphorus pentoxide without any loss of water. It dissolves readily in ether. If the dihydrate is heated in a current of carbon dio.xide at 98° C. a product corresponding very nearly in composition to the nioiiohydrate, U03(N03)3.H20, is obtained at 160° C. under the same conditions the ankydi ffus salt, U02(N03)2, is obtained. The latter may also be obtained by passing a current of dry nitric anhydride over the tri-hydrate carefully heated at 170° to 180° C. It is a yellow amorphous powder, readily soluble in water with c -olution of heat. It reacts violently with ether. When heated to 200° C. it decomposes and leaves a mixture of uranic acid, UO3.H2O, and uranic anhydride. ... 

---