DE. WALTER WAHL: PHYSICO-CHEHICAL DETERMINATIONS 
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caiiied out. The manometer F is a “ Stahlplatten-Hyclraulik-Manometer,” manu¬ 
factured liy Schilffer and Budenljerg, of Magdel)urg-Buckau, Germany, and is 
graduated to 4,500 kg./cm.^, every division corresponding to 20 kg./cm.^. The 
diameter of this manometer is 30 cm., and the scale is accordingly large, so that 
2 kg./cm.’ may be easily read off on it. A second manometer of the same construction 
can he attached directly to the pressure-transmitting pipe, thus enabling a comparison 
of the manometers. This manometer is graduated to 5,000 kg./cm.^ and has been 
used as a standard. 
The smaller compressor H is a screw compressor with a plunger of 15 mm. 
diameter, moved up and down in the compression chamber, in this case a thick 
walled 1 u’onze tube, directly by the screw I. K is a valve by wliich tlie oil reservoir O 
is shut off from the compressing chamber. L a valve which shuts off the compressing 
chamber from the pressure-conducting capillary tube and the manometers M, which 
then remain connected with the investigation bomb. The manometers M are of 
20 cm. diameter, and graduated up to GOO kg./cm.^, each division on the scale 
representing 1 kg./cin.^. The two manometers are attached to a T-piece of bronze 
by which they communicate with each other and with the compressor. Each 
manometer is further provided with a safety-valve, protecting it against very sudden 
l»ig clianges in pressure by which tliey otherwise might be damaged. Also these 
manometers are of the “ Stahlplatten-Hydraulic-MaiKjineter ” type, and manufactured 
by Schaffer and Budenberg. P is a valve capable of withstanding a pressure of more 
than 4,000 kg./cm.", by which the smaller compressor can be entirely shut off* from 
tlie rest of the compressing machine. 
The pressure-conducting pipes, G, from tlie large compressor, and U (U containing 
tlie valve P) from the small compressor, are connected to the upper part of the steel 
vessel 11, through the top of which the long steel capillary tube S communicates 
with the lower part of the vessel, which thus forms a kind of strong steel bottle, on 
the same principle as wash-bottles. This steel flask or bomb contains mercury in its 
lower part, and as the pipe coimected to the bomb containing the substance to lie 
investigated dips into the mercury with its lower end, the mercury shuts off this 
part of the apparatus from the oil in the compressors and transmits the pressure 
without permitting the contents of the investigation bomb X to come into contact 
witli the oil of the compressors. Oil can thus always be used in the compressors, any 
licpiid being used in the pressure-bomb X. By the screw connection at T the 
investigation bomb is attached to, and detached from, the pressure plant, and this 
screw is the only one of the whole pressure plant which is opened between different 
series of experiments when a new substance is introduced into the investigation 
b(unb X."'^ All the joints l)etween different parts of the pressure apparatus are 
constructed on the principle of a hard, circular steel-edge, being forced by as crew 
* The compressing machine and manometers were manufactured by Messrs. Schaffer and Budenijerg, of 
Magdehurg-Buckau, Germany. 
