DISTILLATION. 



changed in their properties, are capable 

 of being separated from other matter by 

 distillation. 



The process employed for distilling 

 liquid bodies from other matter is sim- 

 ply called distillation ; that, on the con- 

 trary, used to separate solicl bodies, by 

 giving them the elastic form, is termed 

 sublimation. 



The apparatus employed for the first 

 process are of several varieties, suited to 

 the nature of the volatile body. That 

 employed for the distillation of water, 

 alcohol, and the various essential oils, is 

 called a still. It is chiefly made of cop- 

 per, and ought to be so constructed, that 

 as great an evaporable surface as possi- 

 ble may be exposed. Those employed 

 in the Scotch distilleries are in the form 

 of an erect cone, the base of which is 

 about four times the altitude. The va- 

 pour which comes from the still is con- 

 densed in two ways. The first is the 

 oldest and most simple method, but not 

 the most effective, The head, or capital 

 of the still, is so formed, as to have a ves- 

 sel or cavity on the outside, containing 1 

 cold water ; the inside is in the form of 

 a cone, and sometimes of a dome, round 

 the base of which is placed a channel, 

 terminating in a*n inclined beak, or tube, 

 to convey the liquid arising from the con- 

 densed vapour. When the vapour rises 

 up against the conical, or dome-like sur- 

 face, the external water causes it in- 

 stantly to condense, and the drops run 

 down the surface into the channel, from 

 whence they pass into the delivering 

 tube, and thence into the receiver. The 

 other method of condensation consists 

 in letting the vapour pass through a spi- 

 ral tube, fitted into the inside of a tub, 

 which is filled with cold water, and so 

 contrived that the product of the distil- 

 lation shall have no communication'with 

 the external water. This tub, which is 

 called a worm tub, should he supplied 

 with cold water at the bottom, while the 

 warm water, caused by the condensation 

 of the vapour, should be made to run off 

 at the top. 



The apparatus employed for distilling 

 bodies more easily condensible consist 

 of two parts, one called the retort, con- 

 taining the substance to be distilled, and 

 the other the receiver, because it receives 

 the substance raised from the retort. In 

 the distillation of bodies which afford 

 permanent gases as well as condensible 

 matters, in addition to the receiver, a 

 number of connected vessels are employ- 

 ed, constituting 1 what, from its inventor., 



is called a Woulfe's apparatus, in which, 

 what is not condensed, or absorbed in 

 the first bottle, passes forward to the se- 

 cond, and so on to the third and fourth,, 

 till at length the absolutely incondens- 

 able part is received into a vessel called 

 a gasometer. Before the invention of 

 this apparatus, this kind of distillation 

 was attended with great danger, both to 

 the apparatus and the operator, the re- 

 ceiver being very liable to burst, and the 

 fumes being intolerably suffocating. Both 

 these inconveniencies are completely ob- 

 viated by the invention of the Woulfe's 

 apparatus. Sometimes an apparatus call- 

 ed an alembic is used for distillation ; it 

 is generally of glass, and is used for ex-. 

 periments in the small way ; it consists of 

 a bottle holding the substance to be dis-_ 

 tilled, having a dome-like head, furnish- 

 ed with a channel similar to that of the 

 common stile ; indeed, it differs only from, 

 it in not having cold water on the out- 

 side. There are various modes of apply- 

 ing heat in distillation, depending upon 

 the nature of the apparatus employed, ag 

 well as upon the substance to be distilled. 

 The common still, which, being of metal, 

 is immediately exposed to the naked fire 

 since from its tenacity, and its property 

 of conducting heat with, facility, it is not 

 liable to crack, which is not the case 

 with glass and earthen ware. If the ves- 

 sel holding the substance to be distilled 

 be of the latter kind, it is essential to ap- 

 ply the heat very gradually and uniform- 

 ly, and after the process, to suffer it to 

 cool in a similar manner. This is effect- 

 ed in different ways ; the most common 

 of which is the sand bath, whUili consists 

 of a vessel of iron filled with fine dry sand. 

 The retort, or other vessel, is imbedded 

 in the sand previous to the application of 

 the fire ; the inferior conducting power 

 of the sand does not allow the heat to ap- 

 proach the retort, btft in that gradual 

 way which will insure its safety from 

 cracking. The heat must also be more 

 uniform, since any sudden increase, or 

 diminution of the fire, will not so imme- 

 diately affect the retort. 



In experiments in the small way, the 

 lamp will answer every purpose of the 

 sand bath, as the sliding rest containing 

 the retort admits of its being placed at 

 any given distance from the flame. In . 

 addition to this, the Argand lamp can be 

 adjusted by the rack to almost any degree 

 of intensity below its maximum. Ano- 

 ther method of defending the retort from 

 the too rapid effect of the heat consists 

 in coating the outside with a mixture of 

 horse dung and clay, or loam. When a 



