( 634 ) 



vaeuumpump patented by Burckhardt and Weiss has been first used, 



1 think bv Olszewski, for removing the large vohimes of' gas Avhich 

 rise from a bath of liquefied gas at a reduced pressure. We shall 

 now speak of some modifications and auxiliarv apparatus bv means 

 of which the perfect purity of a gas is secured in a high vacuum. 

 A pump arranged in this way may also be introduced into circula- 

 tions of costly gases. In our laboratory it has been worked very 

 satisfactorily for many years. A diagrammatic figure of the entire 

 BuRCKHARDT-pump has been given on plate \l Ba. Vac, the pump 

 cylinder with its slide valve box, the beginning of the suction- and 

 the delivery tubes with the auxiliary apparatus belonging to them 

 are shown on plate VIII, where fig. 1 gives the side elevation, fig. 2 

 the top elevation and fig. 3 the section. The well-known working 

 of the piston and the valve, the successive communication of the 

 valve ports 5 and 5', each individually by means of the slide hole 



2 with the suction valve port 1 or with the delivery valve port 4 

 and together by means of the ringshaped opening 3 may be seen 

 without further comment from the section. The pump displaces 

 360 M' an hour, hence, ^^ hen exhausting at a pressure of 2 cm., 

 about 10 M' gas, measured normally can circulate. At Leiden it is 

 used almost exclusively with an additional vaeuumpump exhausting 

 at the compression side. It exhausts then till 2 m.M. 



As a lubricant and for the airtight fittings to be described in the 

 following pages, only bone-oil is used which after having been tested 

 at the exhaustpum[) has proxed to have no perceptil)le vapour pressure. 



For the technical work ordinary ring packings are quite sufficient, 

 I have, however, replaced them by folded packings as described in 

 Comm. 54 Jan. '00 for the compressor and the auxiliary compressor. 

 The leather ring of the i)acking is supported there as in Plate lY 

 h^^ by the India rubber ring h^.^ (for an exhausting packing comp. 

 E^^ PI. YII fig. 3 Coinm. 54). The packing cylinders have been made 

 long enough to contain two folded ])ackings (one for exhausting and 

 one for compression) and a l)ronze tightening piece, but as a rule 

 they only hold the packing for exhaust. 



New additions are the vessels 0^ and 0^ see also plate 11 filled 

 with oil (or with glycerine for those gases which cannot be used 

 Avith oil); they serve to protect the packing cases of the cylinder 

 and the slide valve box entirely from the atmosphere and also to cool 

 the piston rod. The covers ö^ and 0^, protect the lubricant against 

 dust or moisture. 



For the oil holders S^S^ WQ have chosen the construction explained 

 in detail in fig 7. ^S'l.^ is an ordinary oilpot for visible cylinder lubri- 



