( 666 ) 



chiüip, iiuiny appciratus lia\T hecii recommeiidcd hy various iiivcsti- 

 gator-s in order to effect this purpose iiutomaticiilly ^). 



As, however, tliese apparatus are either somewhat eoiupheated or 

 else do not always eifect a satisfactory regulation of the pressure, 

 and as I had very often to carry out distillations under reduced 

 pressure, I have tried to construct an ap[)aratus which would suit 

 my purpose. I have used this apparatus ft)r a year aiul a half 

 and it quite satisfies my requirements. 



The apparatus may be used for any ))ressure situated between that 

 of a column of mercury of a few m.m. and one of about 600 m.m. 

 in height; the required pressure is ke[»t fairly accurately constant. 



For the sake of clearness, the lower half of the annexed drawing 

 represents a section of the aj)paratus and the upper half gi\es a 

 view of the latter. 



A is a glass lul>e witli an intei'iial diameter of about 19 mm. and 

 to which is sealed a tube /> '2 mm. wide: H is a trap-bulb; ('a 

 manomctei' tid)e which stands in the same mercury ^■essel as the 

 barometer I). .1 is attached to the wooden piece C which may be 

 moved in -a vertical direcliou between the pieces F. The tube ..4 

 may be uioxed upwaids and downwards by means of a wheel. ^1 is 

 placed in a vessel [lartly tilled with mercury; the lower opening of 

 A is closed with an indiarul)ber stopper having a vertical hole of 

 about 5 mm. (bameter. To the extremity of the thin tube JJ a [)iece 

 F is connected; £ is made of wooil, coi-k or rubber and has a 

 vertical perforation by means of which it may be pulled over the 

 tube JJ. It has in addition a side /\ (triangular) crevice running as 

 far as the vertical perforation. The proper action of the instrument 

 depends on the piece is". 



Between the tube C and the barometer D is situated a calibi-ated 

 scale movable in a \'ertical direction by means of L, which renders 

 an accurate reading of the pressure possible. From the drawing 

 it is further sho^vn, that .1 and C are connected by meaiis of glass 

 T pieces and of thick indiarubber tubes, not only mutually, but also 

 with the airpump and the space to be e\acuated. (So as not to 



') Kamerlingh Oxnes, These Pi-oc. June 1903 

 Staedel & Hahx, Liebigs Ann. 195 p. 218. 

 GoDEFROY. Ann. Cheni. Phys. [6] 1884 — 1 — p. 138. 

 Auger. Bull. Soc. Chem. [3] 1898 — 19 — p. 731. 

 Hausser. Bull. Soc. Chem. [3] 1899 — 21 — p. 253. 

 Bertraxd. Bull. Soc. Cliem. [3] 1903 ^ 29/3U — p. 77G. 



Chem. Cenlr. 1903 — 2 — p. Oil. 

 A. Smits. These Proc. 27-11-1897. 



