i^'46 



SYNTHESIS OF DKPSIDES. 



Hydrolysis was then undertaken with dilute sulphuric acid 

 in order to separate the sugar, which was very carefully esti- 

 mated by several methods, from the acid portion of the molecule. 

 Examination and analysis of the osazone proved conclusively that 

 dextrose was present and the acid gallic acid. If the hydrolysis 

 were not completed, in addition to the gallic acid and glucose, a 

 dark coloured substance remained, which was called the tannin resi- 

 due. As a final check, artificial mixtures of gallic acid and dex- 

 trose were also made and similarly treated. The acid used was 5 

 per cent. HoSO^Aq, but in one case, Strecker's method, using 

 II per cent. HoSO^Aq, and heating for 24 hours at 400° was 

 employed. The results obtained are shown in the following 

 table : — 



riiese ex])eriments lead to the conclusion that in tiie i)urest 

 tannin investigated i mol glucose is combined with about 10 mols 

 gallic acid, and no other phenol carboxylic acid is present. In 

 order to elucidate its structure still further, an attempt was made 

 to isolate intermediate i)roducts, but this was found to be im- 



