GAS

GAS

( 530 )

full of the fame, to introduce under the mouththe tube of a proof bottle, and to throw up asmuch air as will expell about half the water fromthe phial; then keeping the finger clofe uponthe mouth of the phial {hake it very violentlyfor a minute or two, and fo much of the gaswill be abforbed as to produce a very fenfiblevacuum in the phial. But as large quantitiesof aerated water cannot be prepared in this way,fome machine is required to prefent fueceflivelyto the fame portion of fluid a frefh fupply ofgas, till it is as fully faturated as can be doneunder the degree of preflure employed.

The machine invented by Dr. Nooth, andknown by the name of Nooth’s Apparatus, haslong been in common ufe for this purpofe, andthough it has fome defe£ls, it is on the wholea very ufeful apparatus. This machine, PI. III.Fig. 46. confifts of three veflels; the loweft, a,has a very broad flat bottom, that the whole may{land fteadily. It contains the materials fromwhich the gas is given out (marble dull and di-lute muriatic acid for example, when a carbon-ated liquid is to be prepared, which is mollcommonly the cafe) of which a frefh fupply isfrom time to time to be added through theopening made for that purpofe, the Hopperof which muft fit very accurately. Thegas paffes through the valve b, into theveflel c, which contains the liquor to be im-pregnated. A fedtion of the valve is repre-fented feparately in Fig. 45, and confifts of aportion of a giafs tube b, open at bottom, andclofed at top,'but perforated with feveral fmallholes, and which fits clofely into the bottom ofthe veflel a a, that contains the liquor. Theinner part of the tube b, is partly filled with twothick pieces of giafs tube (reprefented by thedeeper {hading) with the. fmall perforations cand e . The fpace between thefe two pieces isoccupied by a giafs valve in the form of a plano-convex lens, which lies flat upon the lower pieceon which it fmoothly fits, but is eafily lifted upby the influx of gas from below, fufficient toallow it to pafs; whilft it is fo far confined thatit cannot be turned over, but immediately fallsdown again in its proper place.

The middle veflel c (Fig. 46) has a giafsftop-cock to draw off the liquor, and into itdips the end of an upper veflel d, which isintended to afford a fmall preflure on the gas in

and alfo a conftant circulation of the liquorfrom one to the other. At the top of cl is aHopper, which is the only joining of the wholeapparatus which is not required to fit verytight, as it is only intended to allow the excels

of gas to efcape; and indeed it fhould fit ratherloofely, otherwife it allow r s fo great a quantityof gas to collect within, that when it is forcedup it is often projected to fome diHance. Aloofe cork anfwers as well. In ufing this appa-ratus, fo much liquor fhould be poured into themiddle veflel as to rife fome way above thebottom of die tube of the upper veflel that dipsdown. The gas being then generated in thelower veflel a, it rifes through the water of c,up to the juncture between c and d, where, notbeing able to efcape, it accumulates, and by itspreflure caufes the liquor to flow through thebent tube into d, driving before it the atmof-pherical air. When the liquor has thus fallenin c, below the level of the dip of the bent tube,the gas rifes through this tube, and in its pafiageagitates the liquor in d, and fends down a por-tion ; and thus a conflant agitation is kept upwhich highly favours the abforption.

The chief inconvenience of this machine isthe number of parts of which it is formed, andthe accurate grinding required for all the piecesthat fit, which makes the apparatus expenfive,and not eafily repaired when any portion isbroken.

A much Ampler, cheaper, and equally goodapparatus is that reprefented in PI. III. Fig. 47.invented by the late Dr. Hamilton. It confiftsof three parts, a is a tubulated retort, with afhort thick neck, fitting accurately into the de-canter-fhaped veflel b. The retort contains thefubftances whence the gas is procured, and hasthe advantage over Nooth’s apparatus, in allow-ing heat to be applied, fo that it will ferve formaking liquid oxy-muriatic acid, and for manyother purpofes.

The upper veflel c fits into the decanter, andbefides has a long giafs tube proceeding fromthe bottom, and ground accurately to it, whichreaches to the bottom of b, The veflel c fhouldhold about as much as the decanter. The ufeof this apparatus is obvious. The decanter isfirft filled with the water to be faturated nearlyas high as the point where the retort enters,and the advantage of the decanter-form is thatvery little common air is then left in. Theinflux of gas from the retort accumulating at thetop of b drives the contained liquor up the tube d,into the veflel c, till the decanter is quite emptyof water, and only filled with the gas, on which aconfiderable preflure is therefore always keptU P-

This apparatus is not readily deranged, itsparts are ftrong and Ample, and it will bear asmuch fhaking as Nootfi’s machine, care being