Eudiometer tvUJi Sulphuret of Poi-JJb, "XSq 



AB, Plate XII. Fig. 2. reprefents a very fmall ghfs retort, with a long neck, Tts whole 

 capacity being from 12 to 15 centilitres (between leven and nine folid inches Englifli). It 

 mull be chofen of fuch a curvature, that, vi-hcn the neck is fet upright, the bulb may form at 

 its lower part a cavity to retain the matters introduced. 



The extremity of the neck of this retort is ground with emery to enter the glafs tube CD, 

 which is open at both ends, and about 20 or 25 centimetres in length (eight or nine inches 

 Englifli). The retort then clofes the tube in the manner of a ground ftopper, and intercepts 

 all external communication *. 



A cylindrical glafs veflcl, F, is provided, of the form of a common jar, in which the glafa 

 tube CD may be entirely plunged beneath the level of the water. 



Laftly, the fulphuret of pot-afli is prepared and broken into pieces fufflciently fmall to 

 te introduced into the retort. Thefe are to be enclofed, dry and even hot, in a bottle for 

 »fe. 



Thefe conftitute the whole apparatus and preparation of materials. 



When it is required to examine an aeriform fluid, by feparating its refpirable part, two 

 or three pieces of the fulphuret, of the fize of a pea, are put into ^he retort. It is then 

 filled v/ith water, taking care to incline it (b that all the air may pafs out from the bulb. 

 The orifice of the retort is then to be clofed, and inverted into the pneumatic tub, in order- 

 that the gas propofed for examination may be transferred into it in the ufual manner. 



By an eafy manoeuvre of alternately inclining the retort in different diredions, ail the 

 •water is made to flow out of the bulb in which the fulphuret remains. 



"When this is done, the retort is placed in the vertical fituation, and its extremity intro- 

 duced into the tube of glafs CD, which muft always be under water. A fmall lighted' 

 taper is then to be placed under the bulb. 



To fupport the retort in its pofition, the jar is provided with a wooden cover, in which 

 there is a notch to receive it. 



•The firft imprelTion of the heat dilates the gafeous fluid fo much that it defcends almoft' 

 ■ to the bottom of the tube, which is difpofed exprefsly for its reception ; otherwife the 

 partial efcape would prevent an accurate determination of its change of bulk. 



But as foon as the fulphuret begins to boil, the water quickly rifes, not only in the inferior 

 tube, but likewife in the neck of the retort, notwithftanding the application and even the 

 jncreafe of the heat. 



If the fluid be abfolutely pure vital air, the abforption Is total. In this cafe, to prevent 

 the rupture of tlsc vefTel by too fudden refrigeration, the afcent of the water muft be 

 rendered flower, cither by removing the taper, or inclining the retort f; which will not pre-- 



■"-Ciiiicn ChaulTicr liad before confttuSctl, for eudiomctric experiments with phof|)hoFUs, an appnialus little 

 diScrcnt from this, compofcd of a long tube of a fmglc piece, one ttul of which is bended and blown into a bulb, 

 and has al e a prtjjcfting tube, which is clofed with a cork , after having caiifcd the water to rife wiilyn thi; 

 Mbc to about onc-thini of iii height. This inftrument m.iy nilb be applied for experiments with the fulphuret 

 of pot-aOi. I muft obferve, however, that the prailicc is not fo K-!S'^ as it appears -M firft fight : befiJes which, ■ 

 if the pro'^£tin^ tube renders it very convenient fur operating on the air uf the atmofplierc, it is not the fanis 

 with regard to the uhcr gafes, which cannot be introduced but by transferring them. C>. 



\ It docs not appear that inclining the retort would diininiOi ilie rapidity of afccnfion. If the pcrpcndrcul.ir 

 he ijjht were incrcafcd, by partly raifinj; liie lube ubuvc tUt wutii, cc if the ajieituie were partly clofc J, this eflcdt 

 would ffcllo'.v. N. 



Ten^ 



