HEAT. 



being brought into contact with cold 

 surfaces, is deprived of its latent heat, 

 and condensed into a liquid: this is 

 effected, when the process is carried on 

 upon a large scale, by making the 

 vapour pass through a descending 

 spiral tube, which is technically called 

 a worm, and which is immersed in a 

 large quantity of cold water frequently 

 renewed. 



As the varieties in the process of 

 distillation are very numerous, it is not 

 intended to describe them here, but 

 only to explain the general principles. 

 The following experiment will assist in 

 explaining the important but simple 

 process of the distillation of alcohol. 



Ex. Into a glass alembic a, (Jig. 

 22,) put a mixture, composed of one 



Fig. 22. 



part spirit of wine, and seven or eight 

 parts water, coloured with a little 



tincture of litmus or sulphate of indigo. 

 But before it is put into the alembic, 

 light a piece of paper, and plunge it, 

 while burning, into the mixture ; the 

 flame will be extinguished : this will 

 prove that the mixture is uninflammable. 

 Apply the heat of a spirit-lamp 6, and 

 in a very short time the lower part of 

 the distillatory apparatus will become 

 dim with moisture ; a portion of the 

 alcohol will be raised in vapour, and,, 

 coming into contact with the sides of 

 the vessel, will be condensed, but this 

 vessel will very speedily become too 

 hot to condense the vapour ; it will then 

 ascend into the capital of the alembic c, 

 and being there condensed by the 

 coldness of its sides, will run down 

 into the groove, and from thence into 

 the receiver d ; when the upper part of 

 the apparatus becomes too hot to 

 effect condensation, the vapour will 

 pass into the receiver and be condensed 

 there. In a short time after the co- 

 loured mixture boils, a small quantity 

 of a pure, colourless liquid will be ac- 

 cumulated in the receiver ; if this liquid 

 be poured into a saucer and a piece of 

 burning paper be applied, it will take 

 fire and burn to dryness. Thus, it will 

 be proved that from a coloured, unin- 

 flammable mixture, a pure, colourless 

 inflammable spirit may be obtained by 

 the process of distillation. 



A very useful form of still is re- 

 presented fig. 23 : a, is the furnace ; 

 b, the capital of the copper still ; c, a 

 part of the chimney ; d, the worm-tub, 

 containing cold water for condensing the 

 vapour that enters the spiral tube. 



Fig. 23. 



