570 Mr. V. H. Veley and Dr. A. D. Waller. [June 17, 



acid, as these salts under these conditions are nearly completely hydrolysed 

 into their acid and basic constituents.* The above results are summarised 

 below : — 



Caffeine. 



Concentration. 



Time of abolition in 

 minutes. 



Normality. 



Per cent. 



«/100 



0-2 



4-0 



n/200 



0-1 



11 -5 







10 -5 



» 



)} 



11 -0 





»» 



14-0 



Caffcotannic Acid. 



A sample of this substance (Merck), a brown gummy material, as previously 

 described, was made up to n/100 concentration (0"32 per cent.) in normal 

 saline, but was found to be practically inactive. A solution of double the 

 strength (n/50 or 0"65 per cent.) produced abolition in 21 minutes, the record 

 resembling that of caffeine. By way of comparison a solution was made up 

 of n/100 (= 0*2 per cent.) caffeine and 0-5 per cent, of a sample of tannic acid, 

 presumably obtained from oak-bark ; the time required for abolition was 

 20 minutes, namely, five times longer than that for caffeine of the same 

 concentration by itself. The record can be characterised as a retarded 

 caffeine record, suggesting that the free tannic acid added to the caffeine 

 causes some secondary or retarding chemical change. 



Thcohromine {Dimcthyldioxypurine). 



All the records obtained with this base were similar in type, and resembled 

 those of caffeine; in the record given (fig. 2) for a theobromine solution of 

 n/200 (or 0*09 per cent.) concentration, abolition took place in G*5 minutes. 

 The results obtained are summarised as under : — 



Theobromine. 



Concentration. 



Time of abolition in 

 minutes. 



Normality. 



Per cent. 



»/150 



0 12 



2-6 



w/200 



0-09 



0-5 



»//300 



0 -06 



8 -5 



If 



0 06 



9-0 



* Schmidt, ' Annalen,' 1883, vol. 217, p. 284 ; Veley, ' Journ. Chem. Soc. Trans.,' 1909, 

 vol. 9.3, J). 004. 



