and Magazine of the Ceylon Agricultural Society. —January, 1912. 



These experiments thus appear to estab- 

 lish that, complex as the composition of 

 an infusion of the tea may be, it at least 

 yields a definite substance in the shape of 

 caffeine tannate, the composition of which 

 is constantly shown to be one part of caffeine 

 with three parts of tannin. 



The Preparation and Composition of 

 Caffeine Tannate. 

 Caffeine tannate is a very interesting substance 

 apart from its occurrence in tea infusion. It 

 may readily be prepared by mixing aqueous 

 solutions respectively of tannin and caffeine in 

 the cold, when a milk-fluid, sometimes with 

 flakes forming according to the strengths of 

 the solutions, is obtained. If a few drops of 

 carbonate of soda solution be added to the 

 mixture a clear pale yellow solution results. 

 If next a slight excess of dilute sulphuric 

 acid be added caffeine tannate separates in 

 flakes which admit of washing to remove free 

 caffeine or tannin as the case may be. These 

 flakes may be dissolved in alcohol benzene 

 mixture (lto2). On evaporating the solution 

 to dryness a crisp crust of caffeine tannate is 

 obtained. If this residue is taken up again 

 in benzene-alcohol and evaporated over a 

 weighed quantity of lead oxido the two con- 

 stituents are separated. On evaporating the 

 benzene-alcohol and moistening the mass with 

 water to a paste chloroform maybe added which 

 will extract the whole of the caffeine, the lead 

 residue on drying to constant weight will give 

 the amount of tannin as an increased weight ou 

 the lead oxide employed. To give an illustration : 

 A benzene-alcohol solution of the precipitate 

 obtained by adding acid to a solution of caffeine 

 and tannin in weak carbonate of soda was evap- 

 orated to dryness. The weight was 0-1 gramme. 

 The residue was re-dissolved in benzene-alcohol 

 and the solution so obtained was evaporated to 

 dryness in a platinum basiu containing 3210 

 grammes of lead oxide (litharge). The dried 

 mass, after moistening, was extracted with 

 chloroform. The residue (caffaine) from the 

 chloroform, clean and white, weighed 0-025 

 gramme. The lead oxide, after being exhausted 

 with chloroform, was then dried at 120 C. io con- 

 stant weight. The weight proved to be 3 '287 

 grammes, which ropresents a gain due to tannin 

 of 3-287, 3-210, or 0-077 gramme. The 0-100 

 gramme of caffeine tannate was thus split into 

 025 gramme of calfeine and 077 of tannin, 

 figures which account for the whole of the origin- 

 al substance taken, and which give the product 

 3'08 wheu the proportion of tannin is divided 

 by the proportion of caffeine. Caffeine tanoate 

 is readily soluble in boiling hot water, but as 

 the solution cools it turns milky. It is, however, 

 permanently soluble in water containing a little 

 alcohol. If caffeine tannate bo heated with a 

 little water for some time it assumes the form 

 of an oil. 



It was next decided to add an excess of 

 caffeine in solution to a known amount of 

 tannin in solution. If tannin selects a definite 

 amount of caffeine to form a compound it is 

 evident that by estimating the remaining free 

 caffeine in the mixed solution the amount that 

 has combined with the tannin can be ascer- 

 tained. Thus, G-3 gramme of caffeine in solution 



was added to 0'3 gramme of tannin in solution, 

 a few drops of carbonate of soda solution were 

 added to make the mixture quite clear, and 

 then dilute sulphuric acid was added in slight 

 excess. Caffeine tannate readily separnted in 

 flakes from which a clear fluid could easily be 

 poured off. The clear fluid was then repeatedly 

 extracted with chloroform and the chloroform 

 extractions were evaporated. The data and 

 results were as follows : — 



Caffeiue taken ... 0'3 gramme 



Tannin ... ... 0'3 „ 



Calculated caffeine in excess,} 

 assuming that 1 of caffeine > 0-2 gramme 

 combines with 3 of tannin ) 

 Caffeine in excess found ... 0-189 ,, 

 It is difficult to extract caffeine completely 

 from a bulky aqueous solution, but the results 

 show an approximation to a combination of 1 

 of caffeine with 3 of tannin having been formed. 



Next the precipitate obtained (caffeine tan- 

 nate) was spilt up by lead oxide as previously 

 described : — 



Caffeine tannate taken weighed 0'284 gramme 

 Tannin found ... ... 0-214 ,, 



Caffeine ... ... 0"075 ,, 



Total ... ... 0289 



The evidence is here again strong in favour of 

 the existence of a definite compound of caffeine 

 and tannin consisting of one of the former and 

 three of the latter. 



The reverse experiment was next tried — that 

 is an excess of tannin in solution was added to a 

 known amount of caffeine in solution : — 



Tannin taken ... ... -30 gramme 



Caffeine ... ... 0-03 ,, 



Calculated excess of tannin 21 ,, 



The mixed solutions were saturated with 

 ammonium, sulphate and thrown upon a filter. 

 The filtrate was exhausted' with ethyl acetate 

 and the extraction evaporated to dryness (we 

 noted before that free tannin is soluble in satu- 

 rated ammonium sulphate, but that caffeine 

 tannate insoluble). The ethyl acetate gave - 205 

 gramme free tannin against 2 1, calculated. 

 The caffeine tannate formed was again spilt up 

 by means of lead oxide, and there was obtained 

 - 10 yramme tannin and 03 caffeine, a total of 

 0'13 gramme caffeine tannate formed against a 

 calculated 12 gramme. 



Caffeine Tannate Physiologically 

 Considered. 

 We suggest that these findings are important 

 from a physiological point of view, because it is 

 highly probable that caffoino in a state chemical 

 union with tannin must differ very materially in 

 regard to therapeutic action from the alkaloid 

 in a free or uncombined condition, especially 

 having regard to the fact that tannin serves to 

 some extent as an antidote to most alkaloids 

 since it forms with them insoluble compounds. 

 Similarly tannin when combined with caffeine 

 is a totally different thing from tannin in the 

 free state. The astringent properties of tannin, 

 for example, disappear when it is combined 

 definitely with caffeine. It follows that 

 tannin in combination with caffeine will not 

 tan. A solution of pure caffeine tannate does 

 not act upon gelation or proteins, so that 



