192 TANNIC ACID IN WINE. 



This substance, whilst becoming insoluble, unites with 

 the colouring matter, just as albumen and gelatine, 

 which, when put into wine, coagulate, and by precipi- 

 tating the colouring matter, discolour the wine. 



But although albumen or gelatine, if copiously added 

 to young Port wine, almost deprive it of colour, this 

 result is not possible if the colouring matter be pre- 

 cipitated with the apothema of tannic acid. Apo- 

 thema is not quite insoluble in weak spirit, as, for 

 example, in wine ; enough remains in the wine to 

 colour it yellow. Whilst Port wine is forming a 

 deposit, diminution takes place both in the tannic 

 acid and dissolved colouring matter contained in it. 

 The deposit is apothema of tannic acid, which is inti- 

 mately combined with the colouring matter of the 

 wine. As much apothema remains in solution in old 

 Port wine as is found in Madeira, and such liqueur 

 wines, and the colour of the Port wine becomes the 

 same as that of these liqueur wines. 



This explanation entirely agrees with all the reactions 

 which might here serve as illustrations. In the first 

 place, if isinglass be carefully added to very young 

 Port wine, tannic acid and colouring matter may 

 indeed be precipitated, but no yellow colouring matter 

 remains in solution, such as is possessed by old Port 

 wirie ; and further, in Port wine which has been long 

 cellared, a yellow colour is distinctly perceptible after 

 a precipitate of tannic acid and colouring matter has 

 been obtained by the judicious application of isinglass, 



