PLATE CXIX. 



FIG. 334. Screw-press. The substance from which the 

 fluid is to be expressed is wrapped in strong flannel or 

 calico, and the liquid which oozes out is collected as it 

 runs from the small spout. 



FIG. 335. Bunsen's water air-pump. This consists of a 

 wide glass-tube a, into which another tube 6, b', b", passes 

 air-tight, c, is an india-rubber tube connecting a with the 

 water supply, rf, is a clamp to stop the flow of water 

 through c. e t is another clamp to regulate the flow. /, 

 is a reservoir to prevent any water which may accidentally 

 come over from getting into j. a, is a plug to let out 

 any water from /. h, is a screw for connecting a air-tight 

 to a piece of tubing, which should pass 32 feet, if possible, 

 lielow the level of n. i, is a piece of strong india-rubber 

 tubing to connect the air-pump with./, the bell-jar, to be 

 exhausted. The water rushes in at c and down h, carrying 

 bubbles of air with it, as shown ->pp >site , till the exhaus- 

 tion is complete, a is represented as half full of water. 

 *, a funnel tixed air-tight in the india-rubber stopper of j. 

 I, a small cone of platinum foil to prevent the filter 



from being broken, w, a plate of ground glass, n, a beaker to receive the filtrate. N, a manometer to measure 

 tlie degree of exhaustion, o, apiece of platinum foil of the proper size and ghape to make the cone, /. i, a mould, 

 and t, a stamp, to give the proper shai>e to the cone, I. p, is a cone of porous earthenware used as a funnel, q, is a 

 piece of wide india-rubber tubing stretched over the funnel r, and holding the cone p air-tight, r, is a 

 funnel inserted into the stopper of a bell-jar. The bell-jar may either be exhausted by means of a tube in tlie 

 stopper, like.;, or by a tuhnlature in the side, as is supposed to be the case with that holding r. 



FIG. 336. Plantamour's f.mnel for keeping fluids hot during filtration. It may bUo be us, ,1 to keep liquids at the 

 freezing point during filtration, by suKstit iting ice for hot water. There are two kin. Is of these funnels, one of 

 them has simply a wide. . inning above, and anarrow one lielow, which is closed by a cork through hi-h the tube 

 of a glass funnel passes. The glass funnel which contains the filter is thus in direct contact with tin- warm water or 

 ice with which tlie metal funnel is tilled, Tlie other form has a copper funnel in the situation cf thedotted line 

 and in this the glass funnel is placed. The glass funnel is therefore only indirectly surrounded by the water or ice- 

 on the apparatus, and its tem|*rature can therefore not be so exactly regulated, but it can Iieremo\e.l with great 

 facility and another put in its place, which isnot the case when the other form is employed. 



FIG. 337. I)ialy7.ei- of i:utta-;.i'rclia Th.- up]>er figure shows the dialy/er with the parchment paper -tivtelie.l 

 over it. The lower shows it in use floating on water. 



