2^6 Improved Chemical ApparaiuSy ^c. 



them on a true plane, and heating the tube, as exaftlv as 

 I can in the centre between thefe angles, I there form a third 

 angle (C, fig. 4.) while the glafs is foft and yielding *, 

 making it to accommodate itfelf to the ground necks, in 

 which it is left without being moved for about a quarter of 

 an hour to cool thoroughlv. If moved too foon, the tube is 

 apt to alter its form. In this manner, tubes may be bent, 

 one at a time, for a range of any extent ; and when arranged 

 afterwards on anv plane furface, will alwavs be found to fit. 



I {liall here mention a kind of tubes which I have found 

 extremely convenient on many occafions : I mean tubes 

 made of elaftic gum or caoutchouc. They are compofed of a 

 web or tube of wove cat-gut, coated outfide and infide with 

 cla(lic-o:um varnilh. Thev ftand the aftion of moft of the 

 gafes. Ether, alcohol, or oils, however, would deftroy them. 

 The accommodation they yield is very great; as the woulfe* 

 may be agitated or moved in anv direction, and may be 

 placed on the mod uneven furfaces. Thefe tubes are fitted 

 into corks previoufly impregnated with wax or tallow ; and 

 when they are to be made ufe of, I firft put a ring of elaftic- 

 gum (a neck of a gum bottle) over each neck of the woulfe, 

 but fo as to ftand a little higher than the glafs, forming a 

 kind of wall round the cork and tube, to receive melted wax, 

 or lute, to fccure them in their places. 



Defcription of the improved Apparatus. 



Fisr. 1. (Plate VII.) A, the retort joined to a tubulated 

 receiver B. C, the adaptor ground into the neck of the tu- 

 bulated receiver, and fumiflied with a glafs valve made in 

 the fame manner as thofe ufed in the improved Nooth's 

 aoparatus. D, woulfes joined to the adaptor to receive the 

 unabforbed gas : and E, a bent tube to carry the gas that 

 may ftill pafs unabforbed either into a pneumatic apparatus 

 or into a chimney. 



Fig. 2. the valve on a larger fcale, and infcrted in the neck 

 of the adapt ir. It confifts of an internal tube of fmall ca- 

 libre but prettv fiout in fubftance, and ground into an exte- 

 rior tube clofed at the upper end, but perforated with feveral 

 fmall holes to allow the gas to pafs. After the internal tube 

 is ground to fit the external, a portion of it is cut out (as at a) 



* If the tubes are not veiy thick, tie heat from a flare iRmp of tallow 

 and cctton-wick is lufTicient for the purpole. VV'Jicn the tubes are thick 

 I prefer a charcoal hre made in a black Icail crucible, acrdfs which the 

 tubes niay be eafily heated to the required degree. Whichever of thefe 

 methods be followed, the heat (hould not he uppiied too fuddenly ; nor 

 fnould the tubes be blown upon, or expofcd to a low temperature, to cool 

 thenx haltily, as by I'uch treacaicnt they are apt to fly. 



fufficicnt 



