162 VINEGAR, CIDER, AND FRUIT-WINES. 



hose which will allow of the rapid and easy filling of the casks. 

 The vinegar produced is siphoned off into inclined troughs, which 

 deliver it to a central underground tank, from which it is 

 pumped into the storing tanks. 



Malt vinegar generally contains a great deal of mucilaginous 

 matter difficult to settle, preventing its keeping, while giving 

 nourishment to vinegar eels. It is therefore necessary to filter it, 

 and for this purpose it is pumped into the refining or rape ves- 

 sels. These vessels are often filled with wood shavings, straw, or 

 .spent tanner's wood, but nothing acts so well in producing by 

 filtration a clear bright vinegar as the stalks and skins of grapes 

 or raisins technically called " rape." Where there is power and 

 a large quantity of vinegar is manufactured, the filtering is effected 

 under a considerable hydrostatic pressure. The rape is placed in 

 a closed vessel between two false perforated bottoms. A circuit 

 of pipes is connected at the lower and upper part of the vessel, 

 and by means of a pump the vinegar is made to pass again and 

 again through the rape. 



This mode of manufacture is frequently effected by " fielding." 

 In this case, as the term implies, the process is conducted in the 

 open air. The casks rest on strong frames 1J feet high, being 

 supported by firm pillars of brick-work or wood. The operation 

 generally begins in spring and continues during the summer. 

 The fermented liquor is run into the casks by the bung-holes, 

 the latter being left open in dry and loosely covered with a tile 

 in wet weather. Gradually the alcohol of the "gyle," as the fer- 

 mented liquor is called, becomes oxidated, and acetic acid is pro- 

 duced, of course simultaneously affording vinegar. The latter is 

 then drawn off and transferred to the refining or rape vessels 

 where it passes through the process of filtration already described. 

 In some factories large quantities of sour ale and beer are con- 

 verted by similar processes into vinegar, but the product is much 

 inferior to the vinegar made from malt-wort. The large amount 

 of nitrogenous and other extractive substances which those liquids 

 contain undergoes a second or putrid fermentation after the 

 alcohol has been oxidized into acetic acid, and in doing so reacts 

 upon the acid, leaving a liquid of a disagreeable odor slightly re- 

 sembling very stale beer. By the addition of sulphuric acid this 



