Vanillin-hydrochloric acid as a histochemical test for tannin.
Condensed tannin (leucoanthocyanins and catechins) can be demonstrated in fresh plant sections with saturated alcoholic vanillin followed by addition of concentrated HCl. 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 HCl. Some fading and loss of tannin occurs. The phloroglucinol-HCl test for lignin can also be made permanent with this acidic mountant.
D005421:Flavoring Agents; D006851:Hydrochloric Acid; D013194:Staining and Labeling; D013634:Tannins / Q000032:analysis*
D005421:Flavoring Agents; D013634:Tannins; D006851:Hydrochloric Acid