CANE SUGAR. 



of alcohol leaves the retort at a temperature of from 180 U F. to 190 F. and is 

 condensed in the serpentine in the tank j. 



Column Still. In Fig. 279 is given a semi-diagrammatic view of 

 what is known as the French column which is practically identical with 

 Coupler's still ; the column or dephlegmator a is divided into chambers by 

 plates, each of which has a central opening covered by a dome b ; a small 

 overflow pipe c passes from each plate to the next ; the vapours from the 

 boiler d pass upwards through the central openings through the layer of liquid 

 on each plate, and thence through the overflow pipes back to the boiler; the 

 vapours of high boiling point are condensed in the U pipes h in the condenser 

 /, passing back to the still by the pipes g ; a coil i is shown in the tank / 

 where the spirit is cooled. 



Coffey Continuous Still. The coffey still, Fig. 280, consists of 

 two parts, the analyser A, and the rectifier R; either column is built up of 

 rectangular wooden frames resting one on top of the other and the whole kept 

 in position by a number of vertical stay rods. The analyser is divided into a 

 number of chambers formed by the interposition of copper plates b t> } perforated 

 with a large number of holes about in. diameter ; in each plate is a disc valve 

 d d consisting of a disc of copper about 3 in. diameter and opening upwards ; 

 from each plate passes down a dip pipe cc about 9 in. long and 3 in. diameter ; 

 the top of the dip pipe projects about 1 in. above the copper plate and dips 

 into a cup which rests on the next lower plate. The rectifier is divided into 

 chambers by similar diaphragms, save that the five upper chambers are 

 separated from the others by an unperf orated copper sheet n n, which has a 

 large opening atp and a receptacle at o from which leads out a pipe m; the 

 opening at p has a collar 1 in. high ; the five upper plates have no valves or 

 perforations, their object being to cause vapour to pass in a serpentine- 

 direction. 



The method of working is as follows : Wash is pumped into an overhead 

 tank (not shown) and flows down the pipe a a ; this pipe is continuous, and 

 emerging at the bottom of the rectifier is carried to the top of the analyser and 

 discharges the wash over the top diaphragm ; the wash flows down the analyser 

 in a zig-zag direction passing down the dip pipes, which are placed as shown 

 at alternate ends of the plates ; reaching the bottom of the analyser the wash 

 discharges through the pipe Ic. Steam is admitted at a pressure of from 5 to 

 1 Ib. per square inch by the pipe * ', and passes upwards through the per- 

 forations in the plates ; the cups in which the dip pipes stand are always full 

 of wash, and acting as a seal prevent passage of vapour except through the 

 perforations ; the dip pipes projecting an inch above the diaphragms always 

 keep this depth of liquid on the plates ; in case the vapour is unable to pass 



530 



