FERMENTATION 581 



regulated by controlling the temperature. A high temperature causes 

 alcohol to pass off in the cold feint pipes, and at the same time diminishes 

 the condensation of watery vapour so that a weak spirit results ; a low 

 temperature makes alcohol condense below the spirit plate, increasing the 

 quantity of hot feints. To obtain the best results the temperature of con- 

 densed spirit in the spirit plate should lie between 176 F. and 180 F. The 

 control of the stul is effected either by regulating the supply of wash or of 

 steam ; valves are fitted, of course, on both the wash pipe and steam pipe. 

 To enable the attendant to know the strength of the spirit at any moment, 

 a small pipe passing through a supplementary refrigerator takes a sample 

 of spirit from the spirit plate, and conducts it to a locked test case ; if spirit 

 45 O.P. is required, three glass bubbles, one which floats in 42 O.P., one in 

 45 O.P. and one in 48 O.P., are placed in the vessel receiving the spirit ; 

 as soon as all three bubbles rise the attendant knows his spirit is too weak, 

 and when two sink that it is too strong. As a further guide thermometers 

 are placed in various parts of the still ; one in the spirit plate, a second at 

 about the twelfth coil of the rectifier, and a third on the pipe carrying wash 

 to the analyser. 



To use these stills to greatest advantage, they must be worked with as 

 little sudden change as possible. Control is effected by regulating either the 

 flow of wash or steam. In forms of stills where the wash is pumped to an 

 overhead tank, opening or shutting a cock or valve (the latter preferably) 

 controls the flow of wash. In other forms where the wash is pumped directly 

 through the coil a cock is fitted on the pipe, convenient to the distiller, and 

 connected to a second pipe leading back to the vessel from which the pump 

 draws. The amount of steam is regulated by a valve ; in general, it is pre- 

 ferable to control working by the flow of wash. 



The spirit should not be run from the spirit plate too rapidly ; if the latter 

 be emptied by opening the cock too much, a weak spirit collects and the cock 

 must be closed until the test bubbles show that spirit of the correct strength 

 is forming. The supply of w r ash and steam must be adjusted to each other ; 

 too little steam imperfectly exhausts the wash and an excess results in too 

 much watery vapour passing over, giving a weak spirit. To allow the 

 distiller to see that the wash is properly exhausted, vapour from the lees is 

 collected in a separator, and carried through the supplementary refrigerator 

 to a test glass in which are bubbles floating in water and spirit 98 U.P. ; 

 should either of these sink it is certain that the wash is imperfectly exhausted. 

 The advantage of these stills over the common type of vat still lies chiefly 

 in their economy of steam. 



Approximate dimensions of a continuous still of the Coffey type working 

 up 1,000 gallons of wash per hour are here given, the letters referring to 

 sketch in Fig. 358. Rectifier R, total height 24 ft. X 8 ft. x 3 ft. ; analyser 

 A, total height 42 ft. X 8 ft. X 3 ft. ; number of chambers in both analyser 

 and rectifier, 27 ; total length of pipe a a contained in analyser 416 ft. ; 

 diameter of pipe, 2 in. ; total surface of pipe 217 square feet ; size of dip pipes c 

 in rectifier 4 in. x 9 in., and in analyser 13 in. X 3 in. ; diameter of valves 

 d, 5 in. ; diameter of vapour pipe/, 7 in. ; diameter of steam pipe i, 4 in. ; 

 diameter of hot feints pipes h, ij in. ; diameter of spirit pipe, i in. ; dia- 

 meter of cold feints pipe, 6 in. The still described is one constituted of wood 

 and is of rectangular section ; other forms of stills are built throughout of 

 copper and are often of circular section, the wash pipe being worm-shaped 

 instead of straight with U-bends as in this case. 



