APPARATUS.] 



CHEMISTRY. 



is frequently required in some experiments, a mercury 

 bottle is used, into which a bent iron tube has been 

 screwed. The bottle should be about half filled with 



tig. 13. 



to the rapid formation of steam, 

 rangemeuts is represented in Fig. 13. 



the material, and 

 great care should 

 be taken to re- 

 move its outer 

 ori6ce from 

 water, through 

 which the gas has 

 to pass to purify 

 it. lost, at the 

 close of its manu- 

 facture, the 

 liquid should 

 rush back, and 

 so endanger an 

 explosion, owing 

 One of these ar- 



lii many instances, bladders may be used to retain 

 small quantities of gas. A large bullock's bladder should 

 be chosen, and it must be carefully cleaned by means 

 of cloths. The neck is then to be cut off, and a stop- 

 cock introduced into it. The neck of the bladder, and 

 that of the stopcock, are then to be tied tightly to- 

 gether. One of these, fitted 

 with a jet, useful in blow- 

 pipe experiments, is re- 

 presented in Fig. 14. 



In making some gases, 

 powder, &c., is often given 



from the flask, which would injure the bladder and 

 stopcock, and also render the gas impure. This is 



Fig. 14. 



o 



easily prevented by means of a purifier, which may be 

 a wide-mouth bottle with a cork in its neck. Into this 

 two tubes are fitted : that from the vessel making the 

 gas is to reach nearly to the bottom of the purifier, 

 which must be three-parts filled with water ; whilst 

 the tube through which the gas passes into the bladder, 

 is only just to reach inside the cork and neck of the 

 vessel. Connections between the flask, <tc. , may be 

 made by means of short india-rubber piping, which 

 should be a little smaller than the tubes themselves; 

 a little string will fasten the india-rubber tightly round 

 the glass tubes. As the gas passes from the flask it 



Fig. 14. 



water, or in any receiving- vessel. A convenient kind 

 of this arrangement is shown in Fig. 17. Almost any 

 kind of bottle answers for this fi,r. 17. 



purpose. They should only be 

 about half filled with the ma- 

 terials, or the contents might 

 run over, through the tube, 

 and so spoil the experiment. 



The apparatus we have de- 

 scribed will be sufficient for 

 most experiments on the gases : 

 wo shall therefore proceed to 

 mention such as will be required for other purposes. 

 Many substances require to be pulverised ; and for this 

 purpose a pestle and mortar is necessary. Those of 

 Berlin porcelain, and unglazed, are generally useful ; 

 whilst some, for special purposes, should be well glazed, 

 in order that no loss may be sustained by the powder 

 resting in crevices or cracks of the material. Many 

 substances which cannot be powdered in their natural 

 state, may first be heated, and then thrown into cold 

 water. Glass and flint are substances of this kind. 

 Occasionally, as is the case with zinc, some substances 

 must be heated before being powdered. 



Flasks and test tubes are always employed for heating 

 and effecting solutions. But for the purposes of crys- 

 tallisation, during which it is desirable that as much as 



Fig. 18. 



possible of the surface of 

 the liquid be exposed to the 

 air, evaporating dishes are 

 employed. One of these is 

 represented in the annexed 

 figure. The best material 

 for the purpose is Berlin 

 ware; but for ordinary ex- 

 periments, stone-ware, or even watch-glasses, which aro 

 very useful, will answer very well. Tliose having a lip 

 are to be preferred, as that facilitates the pouring of 

 liquids. For some experiments, the inside of the dish 

 should be highly glazed; whilst, for crystallisation, a 

 rough surface is far better. 



A water bath is often required for the purpose of 

 drying precipitates and organic substances ; the object 

 being that their temperature should never rise beyund 

 that of boiling-water. One is easily made by placing a 

 small evaporating dish inside a larger one containing 

 water. The outer one is heated by means of a 

 spirit-lamp ; whilst the inner one contains the sub- 

 stance to be dried. A tin saucepan answers ex- 

 tremely well for the water vessel, as on its rim 

 almost any vessel can be supported. The instru- 

 ment-makers supply such, properly constructed 

 for tlio purpose ; but these possess no advantage 

 over the simple arrangement we have described. 



After solution has been completed, it is often 

 necessary that the liquid should be filtered. This 

 is effected by means of glass or stone-ware funnels, 

 of the ordinary shape, through filters made of 

 proper paper; or, what answers generally as well, 

 common white blotting-paper. Filters, ready cut, 

 may be purchased at the operative chemists; but 



tathe flMk producing th -fM; , the purifier ; c, the tube paising to th & easily made in the following manner : Take a 

 bottom of the purifier; d, the tube through which the gas pussoi to the It. i~'l i- XT 



square sheet of white blotting-paper, as in No. 



1, Fig. 19. Then fold its corners together, as in 

 No. 2 ; again fold its corners, as in No. 3 ; and 

 then open out one fold, cutting oft' the superfluous 

 edges, as represented in No. 4. The filter will then bo 

 complete, but should be moistened with water when 

 placed in the funnel, which facilitates the passage of the 

 liquid to be filtered through it. Ribbed filters are some- 

 times employed ; and they are made by plaiting together 

 the folds of papor in a manner which we cannot properly 

 describe, or illustrate by means of an engraving. 



After a solution is made, the next process is that of 

 testing, or adding to it certain solutions, which will bring 

 out appearances by which the chemist can judge of the 

 nature of the substance under examination. This is 

 effected by means of test-glasses, which are made of 



a U the 

 batten 



blart'ler. 



will bubble through the water, wnich will retain im- 

 purities, and the pure gas will pass on to the bladder. 

 Fig. 16. The above engraving, Fig. 15, illustrates 

 this simple and yet effective plan of 

 purifying gases. 



Some gases, such as hydrogen, do not 

 require heat for their manufacture ; and 

 gas bottles, of two kinds, or one bottle 

 fitted with two sorts of tubes, are used. 

 For experimenting with hydrogen, with 

 respect .to its flame, a straight glass 

 tube, fitted with a cork, and ending in 

 a jet, may be employed, such as is 

 shown in the annexed engraving. But 

 in making hydrogen, carbonic acid, &c., a bent tube 

 i used, so that the lower end may be placed under 



VOL. T 



various shapes. 



For many experiments, ale and wine 

 2K 



