DESCRIPTION OF THE CHEMICAL APPARATUS MOST FREQUENTLYUSED FOR GENERAL PURPOSES, WITHREFERENCE TO THE PLATES.
Acid-holder, pi. i. Fig . i2~vi. 66.
This is a fmall glafs phial, the mouth of•which is clofely fitted, into and inverted overthe neck of a retort or other vefiel, and is fur-nifhed with a glafs flop-cock. Its ufe is to dropany acid or other liquor gradually into a retortor other vefiel in which any procefs is goingon, without admitting the external air or de-ranging any other part of the apparatus. Thequantity of acid dropped in is regulated by theftop-cock.
As the common acid-holders (Fig. 12) haveno communication with the external air, it isdifficult entirely to regulate the fall of the acid,on which account we have given Mr. Pepys ’simprovement to it (Fig. 66) that has anotherglafs Hopper at the upper end, by openingwhich the dropping of the acid may be com-pletely regulated.
ADOPTER, pi. I. Fig. 3.
This is a hollow glafs vefiel of the form of afpindle, the upper part of which receives thebeak of a retort, and the lower part enters theneck of a receiver, as ffiewn in the plate re-ferred to.
Its ufe is to increafe the diftance betweenthe two, and thus to facilitate the condenfation ofthe heated vapour, which is often of importancewhere the vapour is-not readily condenfiblc,and the receiver liable to be heated by the fire.
AIR-HOLDER. See Gazometer.
AIR-FURNACE. See Furnace.
ALEMBIC. See Distilling Apparatus.
This is an old apparatus for fublimation,confiding of any number of earthen pots of theform reprefented, the upper fitting into thelower, and the lowed of all entering into around crucible or any other convenient vefielin which the fubftance to be fublimed is heated.
VOL. II.
Aludels however are now almoft entirely dif-ufed, almod all fublimations being performedonly in two vefiels, viz. the lower one in whichthe material is heated, and the upper, whichreceives the fublimate; it having been found thatwhere aludels were employed, almod all the fub-limate that could be colleHed at all, was de-tained in the firft vefiel; and another incon-venience of aludels is that the fublimed matterif accidentally detached is very liable to falldown again into the crucible.
AREOMETER. See Specific Gravity.ATHANOR. See Furnace.
This is Amply a large glafs globe with a plainneck of moderate length, and anfwers a varietyof purpofes.
BALNEUM. \
BATH. J A bath or balneum inchemidry is (like a common warm-bath) anintermede by which any body immerfed in it,totally or partially, may be heated more uni-formly and moderately than from dire£l contafkwith the fire. The common balnea in chemif-try are veffels filled either with water or fandand fet immediately over the burning fuel.
The Common Water Bath cannot receive agreater heat than 212°, and it will not raife thetemperature of any fubdance immerfed in it,quite fo high. It is fometimes attached to analembic. (PI. II . Fig. 34. b.)
It is particularly ufeful in evaporations ofanimal or vegetable matter, where the productwould be altered and fpoiled by a fcorchingheat, and in fuch cafes an evaporating vefiel fetin any iron pan full of water over a fire, willoften anfwer every purpofe, care being taken tofupply water as it evaporates.
A greater heat is given by the Sand-Bath(PI. I. Fig. 10—VIII. 82—X. & XI. Fig.
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