277 



fitting to the funnel containing the filter, and the water of which 

 is kept boiling by means of a tiibe inserted at the side, and heated 

 by the flame of a lamp beneath. 



F. — Evaporating Apparatus. 



Under this head have to be mentioned dishes of glass and of 

 porcelain, also of tin (see below), loatcJi-glasses, glass beakers of 

 various sizes. 



For accelerating the evaporation at higher temperatures, coals, 

 alcohol or gas, are employed as fuel to act upon the evaporating 

 vessel either directly or divided from it by an ii-on j^lctte or a dish 

 of the same metal, either empty or filled "with sand (sand-hath), 

 or with water (water-hath). 



Should it be necessary to accelerate the evaporation without the 

 application of heat, or under the exclusion of the atmosphere, the 

 air-2yum2y is made use of, and additionally the fluid to be evajjo- 

 rated under the receiver is bx'ought in proximity with either 

 concentrated sulphuric acid or anhydi'ous chloride of calcium or 

 quicklime. 



Some liquids leave, when concentrated to a certain degi-ee, a 

 stifij viscid mass, to dry which entirely in the evaporating vessel 

 is very difficult; but this may be efiected with comparative ease by 

 spreading those substances as thinly as possible on glass plates or 

 on poi'celain dishes. Plates of this kind are, among other instances, 

 indispensable for any contents of filters, which may be expected on 

 drying to stick to the paper, and thus prevent the separation 

 without loss. 



A kind of evaporation is the process of distillation. For this 

 purpose on a larger scale, the tin-still mentioned already under D. 

 is employed. Distillations of ether or of alcohol may be efiected 

 directly from it, but not those of water. For the latter purpose the 

 still has to be furnished with a special contrivance. For instance, in 

 order to obtain, the volatile oil from a vegetable (including at the 

 same time the extraction of the substance), a sieve-like perforated 

 disc of tin and fu.rnished, besides, with a larger aperture of about 

 one inch diameter, is inserted into the still, within one to two 

 inches from the bottom of the vessel. On this disc the vegetable 

 substance, moistened previously with water, but not so as to form 

 a pulp, is spread out, and is subjected to the steam of water 

 coming from the copper boiler, and conducted by means of a tin 

 tube, terminating under the false bottom, into the substance to be 

 distilled. A mechanism of this kind, besides other implements 

 intended for digesting, evaporating, drying, &c., purposes (dishes 

 of tin, &c.), also a refrigerator, together with the tubes requii'ed 

 for supplying the cold, and for removing the hot water, fonn the 

 well-knoAvn Beindoif^s a2)paratus. 



