LABORATORY 



tical neck, for the purpose of permitting 

 absorption, and re-acting, by its contents, 

 against the force required to protrude any 

 gas through the bended tube I K L. 

 Every one of the range of the receiver, E 

 F G, has also two necks, by which they 

 are successively fitted to each other, and 

 each interior neck has a tube of about a 

 quarter of an inch fitted into it, which, by 

 its curvate, reaches nearly to the bottom 

 of the liquid (usually water) placed in 

 each. By this disposition, the usual first 

 product of condensation is received in C, 

 and the purer vapours, proceeding to D, 

 are in part condensed by the water placed 

 therein, and are partly urged through the 

 tube I, into contact with the water in E : 

 and whatever may escape condensation in 

 E, will be urged through the tube, K, into 

 the liquid in F ; and in this manner the 

 operation may proceed through the whole 

 set of vessels, till the gasiform remaining 

 product, if any, shall pass out then beneath 

 the mouth of one or the other of the three 

 inverted bottles at P, which ' are filled 

 with water, and have their mouths im- 

 mersed below the surface of the water, in 

 a dish at the end of the series. S and s 

 are a pair of pieces of wood which serve 

 to support one of the globes, and very 

 conveniently afford an adjustment, by 

 pressing them more or less near together. 

 This apparatus is drawn upon a scale of 

 about half an inch to a foot, which is a pro- 

 per size to be worked by an Argand's 

 lamp ; if it were made larger, the retort 

 would of course require to be supported, 

 as usual, by the parts of the furnace, or 

 otherwise. 



The dish and bottles at the extremity of 

 this apparatus show how the gases or 

 permanently elastic fluids are received and 

 managed. For such gases as are not ab- 

 sorbed by water, a wooden tub may be 

 used, having a shelf therein, at such a 

 depth as to stand a little below the in- 

 tended surface of the water ; or, instead 

 of a shelf, a short-legged stool, loaded 

 with lead, may be used, and in that case 

 any tub or vessel may be used. Jars, or 

 vessels of any convenient figure, being 

 filled with water by immersion, and turn- 

 ing them bottom upwards, may be placed 

 on the shelf, which should have holes in 

 it for the convenience of pouring up any 

 gas, whether from another jar, bottle or 

 vessel, or from the neck or tube of a re- 

 tort, or other apparatus. Jars, &c. thus 

 filled may be conveyed away, either by 

 corking the bottle, or by putting a sau- 

 cer, or other shallow vessel, beneath the 



mouth of the jar, and taking both out to- 

 gether, with water in the saucer. 



Gases which are absorbed by water are 

 usually received over mercury, in which 

 case, on account of the weight, as well as 

 the expence of the fluid, the vessels are 

 made smaller, and the trough has a deep 

 cavity sufficient for immersion, but no 

 larger, and a broad shallow part of the 

 trough supplies the place of a shelf for 

 the jars to stand upon ; and there is 

 an actual shelf at one part only over the 

 end of the deep cavity. Fig. 6, represents 

 a trough for mercury, which may be 

 made of wood or of stone. The space, V, 

 admits the jar, A, to be immersed, and 

 when full it is raised and placed bottom 

 downwards upon the shallow bottom. 

 G is a retort, containing some materials, 

 from which gas, being extricated, rises 

 beneath A, and displaces the mercury. X 

 and Y are grooves, into which one or more 

 wooden shelves may be slided, as occa- 

 sion may require, in which application 

 they are first introduced at the wider 

 part, T, in the plan, fig. 7. 



An apparatus, almost indispensable in 

 experiments on the gases, is a gaxometer, 

 which enables the operator to receive and 

 preserve large quantities of gas with the 

 aid of only a few pounds of water. These 

 vessels are made of various forms, but 

 one of the most simple is shown in fig. 8. 

 It consists of an outer fixed vessel, d, and 

 an inner moveable one, c, both of japan- 

 ned iron. The latter slides easily up and 

 down within the other, and is suspended 

 by cords passing pullies, to which are at- 

 tached the counterpoises, &c To avoid 

 the incumbrance of a great weight of wa- 

 ter, the outer vessel, d, is made double, or 

 is composed of two cylinders, the inner of 

 which is closed at the top and at the bot- 

 tom. The space only of about half an 

 inch is left between the two cylinders, as 

 shown by the dotted lines. In this space 

 the vessel, c, may move freely up and 

 down. The interval is filled with water 

 as high as the top of the inner cylinder. 

 The cup or rim on the top of the outer 

 vessel, is to prevent the water from over- 

 flowing when the vessel, c, is forcibly press- 

 ed down, in which situation it is placed 

 whenever gas is about to be collected. 

 The gas enters from the vessel in which 

 it is produced, by the communicating 

 opening, b, and passes along the perpen- 

 dicular pipe, marked by dotted lines in the 

 centre, into the cavity of the vessel, c, 

 which continues rising till it is full. 



To transfer the gas, or to apply it to 

 any purpose, the cock, b t is to be shut, 



