[Study on the histochemical staining of boric acid]

The detection of boric acid in the tissue is of significance in investigating its toxicity. Because of this, we have devised a histochemical staining method to detect the presence of boric acid. The outline of this method follows. Frozen 12-14 microns sections, cut by a cryostat, are fixed in anhydrous ethanol and stained for 20 minutes in a protonated curcumin solution. Washing in acetic acid follows, and a red stain results if boric acid is present. This method causes a reaction, in which rosocyanin is formed by the reaction of boric acid and the protonated curcumin, and this principle is now used when an analysis of boric acid is needed. As to procedure, a 1 N concentration of sodium hydroxide is dropped onto a part of the stain to be tested, and the presence of rosocyanin is confirmed if the stain turns blue. Consequently, this staining confirms the presence of boric acid.