amino-R acid

Amino R acid is used mainly as an intermediate for conversion to 2-amino-3-hydroxynaphthalene-6-sulfonic acid by caustic fusion at 250℃.

Manufacture of dyes.

The sodium salt of 2-hydroxynaphthalene-3,6-disulfonic acid is aminated by heating with ammonia and ammonium bisulfite for 24 h at 160℃. The charge is added to excess lime and heated to remove excess ammonia, and calcium sulfite is filtered off. The productis precipitated by acidification ofthe filtrate and purified by redissolving the paste in alkali and reprecipitating with acid. The yield is 90 %.