343 



calibrated, lts length is about 600 iiiiu. Another tube D, of equal 

 length, but about 7 nun. in diameter, serves as a connection to 

 the gasapparatus. Tfie capillary tube (■ bears at its top a silver 

 tul)e E, overlapping the tube 6'; it communicates with C l)y means 

 of a silver ca()illary lube, and can eventuall>- be easily removed. 

 The tube 6' is widened at its top-end to about 10 mm., and con- 

 nected with the silvertube in such a manner, that no dust of the 

 room can contaminate the capillary tube C, while at the other end 

 it communicates with a small reservoir R, partially filled with octane ; — 

 this for the pui-pose of preventing, as far as possible, I he evapora- 

 tion of the liquid in C. For this reason R is placed in the same 

 thermostat as the manomeler-tube. The connection of R with (he 

 atmosphere (or with the niti'ogen) is made by means of an adjustable 

 glass lube (t, which opens into a very wide connecting tube leading 

 to a large flask with three mouths, which is provided with dry 

 calciumoxide, with a small manometei-, a tube with drying materials 

 and with a coimection to the nitrogen-holder. In the fig. 1 the oclane- 

 reser\^oir is indicated by C, the silver capillary tube by S, the tliree- 

 mouthed bottle l)y ./. In the same way the manometer is indicated 

 by w, the drying-tube by z^, and the connecting lubes by Qand H. 

 The manometer is arranged in a glycerine-thermoslat of the type 

 usual in dilatometer-thermostats (Könr.KK), however its construction 

 has been varied in some particulars. The thermostats commonly sold are 

 quite unsuitable for this purpose, because they conjmonly show leakage 

 or will show it very soon ; then they cannot be used for glycerine, 

 which was chosen because of its refractive index and low volatility, 

 because this li(piid will dissolve the paste used in setting the glass- 

 windows, within a short time. Two rectangular frames were there- 

 fore made of brass, about 3 cm. broad, and soldered to the thermo- 

 stat. These frames were smoothed as perfectly as possible and 

 possessed an inside furrow about 5 rmn. deep and 1 cm. broad, in 

 which a layer of very thin rubber paste, fixed by a solution of rubber 

 (in carbonbisnlphide), held the two glasswindows fast. Then a second 

 layer of plastic rubber was applied, and the second brass-frame was 

 uniformly pressed against the former with some forty screws. The ther- 

 mostat holds 22 kilos of glycerine, but even after long use it shows no 

 leakage. By means of a toluene-regulator T, a spiral-stirrer ü/ with 

 motor R, and a pair of small burners h^ and b^, the instrument is 

 kept at 25°,1 C. =t 0°,1. L is a thermometer, divided in 0°,1 C. 

 The support F is suspended from the lid H by means of four 

 movable rods /. The manomelertube can then be brought into a 

 vertical position by means of the screws ^i, s^, .v, and s^. Within 



23* 



