228 COLOURING MATTERS IN WINE. 



a little sulphur and oxide of lead mixed with it. The 

 first is dissolved with ether, which removes the fat ; 

 the latter with water, to which a little acetic acid has 

 been added. 



In Port wine, and other such wines as have been 

 cellared and were originally dark, two colouring 

 matters may be distinguished, one of which is the red 

 colouring matter of red wine, and the other the 

 apothema of tannic acid. In order to detect both and 

 separate them, the following method must be adopted : 

 Let Port wine be precipitated with sugar of lead, and 

 a dirty deposit is obtained ; if this be washed, a colour- 

 less liquid flows from it. If the precipitate, after 

 being washed, be suspended in water and filtered, after 

 sulphuretted hydrogen has been conducted through it, 

 the liquid will be tinged with pale yellow. 



The sulphide of lead, when well washed, is found to 

 contain both red colouring matter and apothema. If 

 it be treated with warm alcohol and tartaric acid, a 

 tincture is obtained of the original colour of Port 

 wine, which is redder if the wine be young, or 

 browner if it be old. The colouring bodies are found 

 mixed in it. 



If this liquid, which contains both tartaric acid and 

 alcohol, be digested with chalk, evaporated upon a 

 water-bath and allowed to dry, then treated with 

 water till the last traces of acid reaction disappear, 

 boiled with water and filtered, the apothema is ob- 

 tained as a brown liquid, while the red colouring mat- 



