— 148 — 



not yet had time to make. I seriously doubt, however, whether 

 encouraging results will be obtained. 



The construction of the copper bath is made plain by the figures 

 I and 2 ; it is 24 cm. long, 15 high, and 8>^ broad ; it can be made 

 at any respectable tin shop. This bath stands in a piece of sheet 

 copper bent up at right angles along the sides, as shown in the end 

 view. fig. 2 ; on one side, this vertical part need not be over i cm. 

 high, just enough to project a little up the side of the bath which 

 rests snugly against it, not as shown in the figure ; along the other 

 side it projects upward, at a little distance from the side of the 

 bath, about 15 mm. and to about the height of 4 cm. ; opposite 

 each of the tubes of the bath a slot is cut in this vertical part, 

 which serves then as a shoulder against which the glass tube rests 

 when in place, to keep it from slipping down and out of position. 



The tube, fig. 3, for containing the substance has at the zone a 

 three small projections on the inner surface, which support a per- 

 forated platinum disk of rather heavy platinum foil carrying the 

 asbestos filter. This tube is 13 cm. long and 23 mm. inner diam- 

 eter, and weighs, with its close stoppers, about 30 gms. 



The filter is readily made in the same manner as the Gooch fil- 

 ter, the tube being first fitted to a suction flask by an enlargement 

 of one of the holes of the rubber cork, or, better still, by slipping 

 a short piece of rubber tube over it, of such thickness that it will 

 fit tightly in the mouth of one of the new suction flasks with lat- 

 eral tube for connection with the suction. A very thin welt of as- 

 bestos is sufficient ; if it is too thick the gas and ether will not flow 

 through with suitable ease. 



About two gms. of the substance are put in this tube, previously 

 weighed with the stoppers b and c, and the weight of the substance 

 accurately determined by weighing tube and contents. The stop- 

 pers are removed, a band of thin asbestos paper is wound around 

 the end d of the tube, a little behind the slight shoulder at the 

 rim, as many times as may be necessary to make a snug fit when 

 this tube is slid down into the copper tube in the bath ; thus the 

 circulation of air between the glass and the copper tubes is pre- 

 vented that would retard the heating of the former ; the stopper e 

 is put in the lower end of the tube, for connection with the hydro- 

 gen supply, and the stopper/ in the upper end ; this latter stopper 

 is connected by rubber tube with a glass tube slipping easily 

 through one of the holes of a rubber cork closing a small flask, con- 



