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CONTROLLING THE EXIT AND ENTRANCE OF GASES. 



When fermentation occurs in the open vats, or ''keeves," natu- 

 rally one can not control the contact of air with the surface of the must. 

 But the French, by permitting- the top lees to rest, in a large measure 

 guard the liquor from contact with the air. The reasons for thus 

 guarding- the must do not appear to be recognized by English makers, 

 but are quite generally considered in France, and ver}^ strictly so in 

 Germany. If the must is fermented in closed vessels, it is a very 

 simple matter to guard the entrance from germ-laden air by the use 

 of simple devices such as are shown in the accompanying illustrations. 



In fio'ure ] 5 is shown a device which was found in use to some extent 



c5 



Fig. 15. — Noel device for ventilating fermentation casks. 



in France, the character of which will be quite readily understood from 

 the illustration. The metal base (a) screws into the cask and carries 

 two connected glass chambers {h and c). The metal cap (d) unscrews 

 to allow the entrance of liquid to the control chamber (c). When the 

 cask is tilled to the proper height, the bunghole is securely closed, and 

 this device is either screwed into a small central opening in the bung 

 or into a hole in the cask near the bung. The liquid desired for puri- 

 fying the air — either 8(» per cent alcohol or 10 per cent sulphuric acid — 

 is poured into the chamber {c) until both glass chambers are about 

 half full; then the apparatus is ready for operation. Should the pres- 

 sure decrease in the cask by reason of falling temperature air can only 

 enter by passing through this apparatus in a course contrary to the 



