Vanillin-Hydrochloric Acid as a Histochemical Test for Tannin

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Abstract
Condensed tannin (leucoanthocyanins and catechins) can be demonstrated in fresh plant sections with saturated alcoholic vanillin followed by addition of concentrated HC1. Bright red vanillin-tannin condensates are formed immediately. Preparations may then be made permanent by mounting in a 1:1 mixture of Hoyer's medium and concentrated HC1. Some fading and loss of tannin occurs. The phloroglucinol-HC1 test for lignin can also be made permanent with this acidic mountant.