Barium hydroxide, preparation crystalline

Barium nitrite [13465-94-6] Ba(N02)2, crystallines from aqueous solution as barium nitrite monohydrate [7787-38-4], Ba(N02)2 H2O, which has yellowish hexagonal crystals, sp gr 3.173, solubihty 54.8 g Ba(NO2)2/100 g H2O at 0°C, 319 g at 100°C. The monohydrate loses its water of crystallization at 116°C. Anhydrous barium nitrite, sp gr 3.234, melts at 267°C and decomposes at 270 °C into BaO, NO, and N2. Barium nitrite may be prepared by crystallization from a solution of equivalent quantities of barium chloride and sodium nitrite, by thermal decomposition of barium nitrate in an atmosphere of NO, or by treating barium hydroxide or barium carbonate with the gaseous oxidiation products of ammonia. It has been used in diazotization reactions. 

The baryta solution is prepared from pure crystalline barium hydroxide, Ba(0H)2.8H20, by dissolving in distilled water. Any carbonate is allowed to subside and the clear supernatant liquor syphoned into the storage bottle after the latter has been filled with air free from carbon dioxide. 

D-Mannonic acid was prepared by Fischer and Hirschberger since the calcium, barium and cadmium salts were all amorphous, the crystalline phenylhydrazide was isolated. Hydrolysis with barium hydroxide followed by removal of the phenylhydrazine with ether and the barium with sulfuric acid gave the crystalline lactone. The phenylhydrazide could also be obtained (15% yield) by the oxidation of hydrolyzed ivory-nut meal. D,L-Mannose was converted by Fischer to D,L-mannonic acid and isolated as the phenylhydrazide. 

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