126 DISEASES OF WINE. 



stances which can no longer be precipitated by gelatine. 

 The disease begins by resolving tartaric acid into 

 carbonic acid. The addition of tartaric acid to the 

 diseased wine does not restore the original colour to 

 the wine, but makes it rose-coloured. 



If the disease has not lasted too long, the quantity 

 of alcohol continues the same as in good wine, and 

 these diseased wines may, therefore, be used for the 

 distilling and preparing of brandy. Every endeavour 

 is made to remedy this disease, and render the wine 

 saleable, by the use of alum and tartaric and sulphuric 

 acid. French white wines of good quality are not 

 subject to this disease ; only the red wines are liable 

 to it. The decomposition begins at the bottom of 

 the cask, and is doubtless occasioned by the decom- 

 position of the organic constituents of the wine fer- 

 ment. It is here that the germ of the evil must be 

 sought, for in these constituents is a substance which 

 causes tartaric acid to decompose, and if aided by the 

 air, oxidises it to carbonic acid and water. The wine 

 cannot, therefore, become acid, for the carbonic acid 

 either escapes, or combines with the potash of the 

 cream of tartar. 



The carbonate of potash thus formed changes the 

 red colour into blue and brown, and causes decom- 

 position in the tannic acid, and in the fatty acid com- 

 pounds of the wine upon which its aroma depends. 

 Experience teaches that sulphuric acid and alum, if 

 used early enough, will prevent or arrest this disease. 



