Evaporate to dryness an aliquot portion of the alkaline filtrate (p.
61), treat the residue with 1 or 2 cc. of water, and slightly acidify
the solution with hydrochloric acid. Add about 25 cc. of absolute
alcohol, boil, filter, and repeat the extraction of the residue. Make
the filtrate slightly alkaline with sodium hydroxide, and evaporate it
to dryness. Add a little water, slightly acidify with hydrochloric acid,
and place a strip of turmeric paper in the liquid. Evaporate to dryness
on the steam bath, and continue the heating until the turmeric paper is
dry. If boric acid is present the turmeric paper becomes cherry red. It
is not usually necessary to determine quantitatively boric acid; the
quantitative method devised by Gooch[33] is recommended.