FERMENT OILS. 600 



When the oil is not very volatile, the retort may be surrounded 

 •with water and the vessel containing it very gently warmed by a 

 Bunsen flame beneath it ; the condenser being surrounded with 

 crushed ice. When the liquid is rather more volatile the Bunsen 

 flame is not used, and the retort is surrounded in the vessel V 

 with dry sand. When the oil is extremely volatile the retort is 

 surrounded with crushed ice and the condenser is plunged into a 

 refrigerating mixture, such as ice and salt or ice and crystallised 

 calcium chloride. In such mixtures it is found that a greater 

 degree of cold is produced by employing snow instead of crushed 

 ice, by reason of the finer state of division permitting a more 

 intimate mixture to be made. At the conclusion of the operation, 

 the small tap X, which is carefully fitted in the cork at the neck of 

 the retort, is very gradually opened, so as to allow air to slowdy fill 

 the vacuum. The apparatus is then disconnected, the cork at the 

 neck of the retort taken out, and the residual oil removed. 



When operating on somewhat larger quantities, the apparatus 

 represented by the figure on page 356 is a convenient form. 



The ethereal solution is placed in the still, wdiich has a 

 •conical bottom provided with a tap for withdrawing the residuum. 

 This vessel is enclosed in a metallic cylinder, which may be 

 filled either with w^arm water supplied from a water-heater in 

 connection with it, or with cold water, or it may be left 

 empty, as circumstances require. The connecting pipe is 

 •connected with the body of the still and the condenser with 

 brass unions, through which the pipes pass. The connecting 

 pipe and worm condenser are of tin. At the base of the condenser 

 is a dome-shaped tinned-copper vessel for receiving the condensed 

 .solvent ; this part is provided with a glass " water-guage," 

 by means of w^hich the amount of fluid distilled over can 

 be known. The water pump for effecting the exhaust is attached 

 to the condenser. The operation is conducted as with the smaller 

 .apparatus above described ; air being allowed to enter gently 

 when the solvent has distilled over. The solvent is drawn off 

 by the tap at the lower part of the condenser and the volatile 

 oil by the tap at the lower part or the vessel corresponding 

 to an ordinary still. Stills of this description, termed vacuum 

 stills, are made in all sizes, and more or less modified in structure 

 to suit different purposes and the scale on which operations 



