Note 181 — Part IV. Examination and Analysis of Cacao Preparations.
Reading edition
Merck’s Catalogue of Reacting Agents (2nd. Edition, page 88) gives a convenient method of determining the presence of theobromine and caffeine (Gerard’s reaction). We annex an extract.
Gerard’s Reaction on Theobromine.
A mixture of 0·05 g of theobromine, 3 ccm of water and ccm of soda wash is decomposed with 1 ccm of a silver nitrate solution 10 percent strong, heated to 60 C. and the solution so obtained cooled down. It then gelatinises very perceptibly. Caffeine does not give this reaction.
Cf. Pharmaceutical and Chemical Journal 1906, p. 476. Apoth.-Ztg. 1906, p. 432. Pharm. Ztg. 1906, p. 512. Chemical Leaflet 1906 II, p. 167 among others.