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When the receiver is tubulated it gives theadvantage of allowing all the joinings betweenit and the retort to be perfectly air-tight, with-out danger of the vefl'els burfting by the ex-panfion.

The alembic employed for diftillations inlarger quantities than with the common fizedretorts is reprefented in Pi. II. Fig. 33 and 34;the latter of which is a feCtion of the former.This is taken from a drawing of a very excel-lent alembic made of tinned copper, almoftexaCtly the fame as that given by iieaume inhis Elements de Pharmacie, and ufed by thatexcellent practical chemift. It contains befidcsthe eflential parts of the apparatus the veryufeful addition of a water hath, which may beemployed or taken out at pleafure. This appa-ratus confifts of the four following pieces : a aFig. 33 and 34 is the boiler, which is let in toa portable furnace to the height of the Ihoulder.It has a fmall opening at the upper part, hoppedwith a cork, by which frelh liquor to be diftilledmay be poured in during the procefs of diftil-lation without deranging the apparatus : b b isthe water bath which finks almoft to the bot-tom of a, and is therefore kept entirely fur-rounded with boiling water, c is the capital orpart in which the condenfation of the vapourbegins. It is only feen in Fig. 34 , being hid inFig. 35 by the vefiel d. The capital is of aconical Ihape, and at the lower part of the conea fmall gutter is made by a doubling of thecopper plate, which terminates in a conductingpipe that points obliquely downwards. Thecapital c is entirely inclofed and cemented intothe refrigeratory d, fo as to make but one piecewith it. The ufe of the veffel d is to con-tain cold water, which by cooling the out-fide of the capital c facilitates the condenfationof the vapour within it and caufes it to flow ina ftream down the conducting pipe, e is acock belonging merely to the refrigeratory d, tolet the water off when too much heated by theboiling vapour in the capital. The vefiel d hasalfo two handles, by which it may be lifted onand off more conveniently. This apparatus isfo conftruCted that the water bath b may beentirely removed, in which cafe the capitalwith its refrigeratory clofes direCtly upon theboiler a, which then contains the matter to bediftilled. A capital -and refrigeratory fittingupon a fmall boiler is alfo {hewn in Fig. 35.This is often made of block tin, and is veryufeful in diftilling water for chemical purpofeswith little trouble.

There is however one difadvantage in the

alembic with the refrigeratory thus placed cnthe top of the apparatus, which is, either thatthe water of the refrigeratory foon gets fo warmas not to be able effectually to condenfe all thevapour; or if it is kept conftantly cold, a con-fiderable part of the condenfed vapour dropsback again into the boiler, which is direCtly be-neath it, and thus the procefs is prolonged,befides the danger of altering the quality ofthe product by the long heating. J o remedythis defeCt feveral chemills (and among themBeaume) have added to the alembic a terpen-tine or worm tub (fuch as' is repreftnted in Fig.32,) into which the conducting .pipe of thecapital opens, and it is this addition probablywhich has led to a great Amplification of theapparatus, by removing entirely the 'refrigera-tory round the capital and caufing the whole ofthe condenfation to be performed in the fer-pentine. This forms the common ftill with itsadjoining worm-tub, which is now ufed withfome variety of cowftruCtion almoft exclufivelyin this country both in the large way in the vaftmanufacture of diftilled fpirits, and where onlya few pints of diftilled liquor are wanted, andwhich has, with us at leaft, almoft entirelyfuperfeded the old alembic.

The common ftill, Fig. 31, confifts of onlytwo parts, viz. a the boiler, which is here {hewnas partly buried in a portable furnace ; and bthe head or capital, which confifts of a prettylarge hollow globe, the upper part of which isdrawn out into a curved pipe that makes acompleat arch and terminates at c Fig. 32, whereit enters the upper part of the ferpentine, orworm. This latter is a long pipe made ofpewter, with a decreafing diameter to the bot-tom, and fixed in a tub filled with cold water,which effeClually condenfes the vapour, fo thatthe liquid falls in a thin regular ltream fromthe lower end of the ferpentine. The joiningbetween the boiler and head of the ftill generallyrequires a flight luting, for which flips of paperdipped in pafte, or of wet bladder neatly ap-plied over the circle of junction is fufficient.The line of tube from the bend of the ftill-headto the very bottom of the worm-pipe fliould bea gradual uniform flope downwards, and fomenicety is required in the maker to give the fer-pentine that regular falling fpiral line'which-'isfound the molt favourable to fpeedy conden-fation. The chief ditadvantage of the fpiralworm-pipe is the difficulty of cleaning it andgetting out the remains of any ftrong-imellingfubftance, fuch as an eflential oil; whereas thelarge alembic capital is eafily cleanfed.