DISTILLATION 



is finally condensed by traversing the worm in r (the refrigerator}, whence it is deli- 

 vered at /. At the same time a steady current of the original alcoholic liquor is ad- 

 mitted from the reservoir H, into the exterior portion of the condenser v, by means of 

 the tap, the flow from which is regulated by the ball-cock g. Whilst condensing tho 

 spirit in the worm the wash has its temperature raised, especially in the upper part, 

 and thence it ascends by the tube k into the heater E, by the small orifices h k, J!</. 

 626, where it is still further heated by the current of heated alcohol which has risen 

 into the worm from the still, whilst at tho same time assisting in the condensation of 

 the spirit. After performing its office of condensation, and when nearly at the boiling 

 point, the alcoholic liquor passes out by the tube I, and is conducted to the top of the 

 distillatory column c. Here it trickles down over a series of lenticular discs of metal 

 (shown in Jiff. 626), so contrived as to retard its progress into the still B, and yet per- 

 mit the ascent of the steam. In this distillatory column (c, fig. 628) it meets the steam 

 628 rising from tho still B. The greater part of its alcohol is 



expelled, which, traversing the series of condensers before 

 described, is ultimately liquefied and collected at z ; but, to 

 complete the rectification, it descends into the still B, and, when 

 above a certain level (m m), into A, which stills being heated by 

 a furnace beneath, the final expulsion of alcohol is accomplished, 

 and the spent liquor run off at x. 



The details of the construction of the apparatus employed 

 in the distillation of spirits have been here given, since this 

 process is perhaps one of tho most important of the kind ; but 

 various modifications are employed in the distillation of other 

 liquids. 



In some cases unusually effectual condensing arrangements 

 required, as in the manufacture of ether, chloroform, 



bisulphide of carbon, and bichloride of carbon. 



In others higher temperatures are 

 necessary, as in the distillation of 

 sulphuric acid. 



When the liquids to be distilled are 

 acid, or otherwise corrosive, great 

 care has to be taken especially that 

 tho worm or other condenser is of a 

 material not acted upon by the acid. 

 See ACETIC ACID, and SULPHURIC 

 ACID. 



The term ' distillation ' is sometimes 

 applied to cases of the volatilisation 

 and subsequent condensation of the 

 metals either in their preparation or 

 purification. 



In cases like mercury, potassium, 

 and sodium, where they are condensed 

 in the liquid state, or visibly pass 

 through this state before volatilisation, 

 this term is quite appropriate ; but 

 where tho fusing and vaporising 

 points nearly coincide, as in the case of 

 arsonic, tho term ' sublimation ' would 

 be more suitable. 



Nevertheless, it is difficult to draw 

 a precise line of demarcation between 

 tho two torms ; for, in tho cases of 

 zinc, cadmium, &c., the metals being 

 melted before volatilisation, and con- 

 densed likewise in tho liquid 01 

 tho term is certainly correct. 



F'.r tho details of construction of 

 the distillatory apparatus we must refer to tho articles on these several metals. 



Distillatio per descensujn is a term improperly applied to certain cases of distillation 



where the vapour is dense, and may l.e collected by descending through a tube which 



has an opening in tho top of the distillatory vessels, and descends through tho body of 



the vessel in which the operation of evaporation is going on, being collected below. 



This is clearly merely due to the fact of the vapour being even at a high tempera- 



