" Casse " IN Wine. 57 



Rhodoganeine and Cyanoganeine have often been confused 

 under the name of CEnocyanine. According to Bouffard this matter 

 has the property of turning red under the influence of acids, and 

 blue under the influence of alkalis. This would seem erroneous in 

 view of the fact that Jacquez wine, known for its blue colouration, 

 often contains a greater proportion of acids than red wines. 



Pheoganeine is generally admitted by oenochemists — Bouffard, 

 Roos, Martieu, etc. It is due to the absence of the two other colour- 

 ing matters that very old wines owe their yellow straw colour. 



With the object of studying these three colouring matters, the 

 three following wines were selected : — • 



1. Tinturier wine (Pontac) — Rhodoganeine predominating. 



2. Jacquez wine — Cyanoganeine predominating. 



3. And very old wine — Pheoganeine predominating. 



These wines were treated with tribasic acetate of lead. The 

 precipitate placed on a filter was washed several times with distilled 

 water, until the filtrate ceased giving a precipitate with ammonia. 

 The pre(.:pitate was then heated with sulphuretted hydrogen, and 

 again filtered. In the filtrate we had the colouring matter mixed with 

 HoS, which was liberated bv reduction on a water bath at about 

 40OC. 



The following are the reactions of acid, alkali, and oxygen on 

 the three solutions : — 



Acid (weak sol.) intensifies the colour of Rhodoganeine, turns 

 Cyanoganeine red, Avithout action on Pheoganeine. 



Alkali (weak sol.) turns Rhodoganeine blue, without action on 

 Cyanoganeine and Pheoganeine. 



Oxygen turns Cyanoganeine yellow, Rhodoganeine slightly 

 yellow, without action on Pheoganeine. 



These mav be condensed in the following table : — 



Coi-oiK. Acn)s. 



Alkalis. 



Rhodoganeine Intensifies Colour Turns Blue 



Cyanoganeine Turns Red 1 Without Action 



Pheoganeine Without Action [ Without Action 



Oxygen. 



Turns Yellow 



,, slight Yellow 

 Without Action 



Pheoganeine is therefore the most stable. Concentrated acids 

 and alkalis are without any action on it, while they turn the two other 

 colours brown, and decompose them. The " mutage " (discolouring) 

 of wines is based on this property. 



If 20c. c. of red wine are treated by loc.c of pure SOo H4 the 

 reaction is very marked. The solution diluted with water and filtered 

 will contain Pheoganeine in solution. 



This solution saturated with Carbonate of Baryte, filtered and 

 concentrated in a vacuum, will give a pure solution of Pheoganeine. 



Yellow wines, such as those used in the manufacture of Ver- 

 mouths, are unaffected by precipitating reagents, for they only 



