EUD

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For diftillation of fmall quantities of eafilycondenfible iubftances, where much nicety anddeanlinefs is required, the glafs alembic, Fig.39, is highly ufeful. It confifts of two pieces,viz. a the cucurbit or boiler, the bottom ofwhich is .made thin fo as to bear a lamp-heat,and b the capital. Thefe are fometimes madetight by luting and fometimes by grinding. The.beak of the capital may pafs into the glafs bal-loon c or into any other convenient veiTel, whichlaft may alfo be furrounded with cold water orice, if required. The glafs alembic is in fomerefpects better than the retort and receiver,inafmuch as the vefiel to which heat is appliedcan be got at much more eafily to be filled orcleanfed, but it is an expenftve apparatus andliable to accidents.

The old veffel called the Pelican Fig. 38, isa kind of alembic fo contrived as to allow thediftilled liquid to fall down again perpetuallyinto the veffel whence it was expelled. Animprovement on it, Fig. 37, is of the famekind. See Pelican.

DOME is the upper part of feveral kinds offurnace, round which the flame of the fuelreverberates before it enters the chimney. SeeFurnace.

EUDIOMETER.

The various proceffes belonging to Eudiometryor the afcertaining the purity of the air havebeen mentioned under that article in the for-mer part of this work. Some of the moil con-venient veliels for that purpofe may be heredefcribed.

PI. I. Fig. 18. is a graduated jar for mea-furing gaffes. It j s made wider at bottom tohand more fteadily. There are two ways ofgraduating jars, either of which any one mayreadily perform for himfelf. Seledt a veryfmall phial or tube which will exactly hold,when brimfull, an aliquot portion of a cubicinch, which is determined by weighing thecontents, allowing for the cubic inch at 6o°temperature 252-! grs. of diftilled water. Fillthe eudiometer jar with water at 6o° invert theempty phial under it, and turn it up whenwithin the jar, by which means the requiredportion of a cubic inch of air will rife to thetop of the jar. Pafte a long flip of paperround the level of the water in the jar, andthen repeat the fame operation till the whole isgraduated. The lines may then be markedwith a diamond, or a fine three-cornered file,and numbered, and the paper feraped off.

In graduating a jar in this method there is alittle trouble in getting a. phial to hold the gre-

cife quantity, and it will be more accurate Ifthe rim round the neck is taken off andthe edges ground fmooth. If the requiredweight of water does not quite fill it, a fmallpellet of wax or cement may be added, and thismay afterwards be melted upon the bottom of'the phial to diminifh its capacity. In gradu-ating a jar in this manner, the hand of the ope-rator fhould touch the phial only for an inftant,and at the thickefl part of the glafs, to avoidthe expanfion of the contained air by the warmthof the hand.

Another method of graduating is to weigh inthe jar itielf fucceffive portions of diftilledwater correfponding with the divifions of the cu-bic inch intended to be marked, and to (cratch-the levels by the file or a diamond. This isin fome refpefts more accurate than the former,as, with tolerable care, it obviates all danger ofany fenfible error from accidental changes intemperature, the whole meafurement being-made with water in which the difference of a •.degree or two is fcarcely felt. There is onlythis circumflance to be obferved, which is, tocarry the lines of divifion nearly round thewhole circumference of the jar, otherwife fomedeception may eafily arile in the ufe of it, un-lefs the furfaces of the top and bottom'of thejar are exadlly parallel to each other; for when-graduated by fucceffive quantities of water, it isobvious that the jar muff ftand on its clofedend, and the contrary when graduated by por-tions of jir.

The above inftrument is (imply a graduatedjar, and therefore fomewhat improperly calledan eudiometer jar, but two or three diredt eudi-ometrical veflels have been contrived wherebythe fubftance intended to analyze the containedair by abforbing a portion may be convenientlyapplied to it.

Dr. Hope’s eudiometer is the following:PI. IV. Fig. 55.

It confifts of two parts, the lower of which.isa fhort thick bottle with an upper and a fideopening (the latter doled by a glafs ftopper)and the upper part is a graduated tube clofedat top. and accurately fitting into the lowerbottle by grinding. To ufe it, take off the tubeand fill it quite full with the gas to be exa-mined, and alfo fill the bottle with the eudio--metrical liquid (fulphuret of lime for example)and without fhaking it, fink it in water. Then,immerfing the open end of the tube in the fame-vefiel, bring it over the bottle and thruft it in.The bottle and tube may-then be taken out, and-well fhaken, that the liquor may thoroughly,