Food and Drug Regulations

B.06.050 [S]. Indigotine shall be the disodium salt of indigotine-5,5′-disulphonic acid, shall contain not less than 85 per cent dye, as determined by official method FO-7, and may contain not more than

• (a) 0.2 per cent water insoluble matter, as determined by official method FO-8;

• (b) 0.4 per cent combined ether extracts, as determined by official method FO-9;

• (c) 1.0 per cent subsidiary dyes, as determined by official method FO-10; and

• (d) 0.5 per cent intermediates, as determined by official method FO-11.