Azosalicylic acids

The pure reddish brown solution is filtered to remove copper oxide, and the azosalicylic acid is precipitated at 80°C. by the addition of 15 per cent hydrochloric acid. The product is insoluble in water. The yield is about 28 grams, or 90 to 95 per cent of the theoretical amount. From 156 grams of pure chlorobenzoic acid, 230 grams of pure azosalicylic acid can easily be obtained, whereas with impure starting materials and incorrect reduction of the nitro compound, the yield may fall to less than half this value. 

A third is the chromium complex of alizarin yellow 2G, one of the large group of azosalicylic acid metal complexes 25) ... 

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