(33) 
produced in the supply of gas. As E. Bose 1) has also demonstrated, the 
chief requirement for this is a large volume with an extensive surface 
and well conducting walls, while the liquid must have a large 
coefficient of expansion «, small coefficient of compressibility @ and a 
small specific heat and must be forced up in a rather narrow tube. As 
an additional requirement might be mentioned the regulation of the 
exterior pressure of gas by means of a manostate, as used by Smits?) or 
by TrauBe and PrNcussoHN %) but as for my apparatus the regulation 
of the gas supply was sufficient, I could neglect this. 
The liquid used by me was xylene; Bose advises the use of 
chloroform, for which B = 0.064, specific heat = 0.235; xylene 
a 
however is less dangerous, while — = 0.075, and is in that respect 
a 
almost as advantageous. The xylene is enclosed in a copper thin- 
walled spiral A, consisting of 3 layers each of 6 turns; the whole 
length is 12.5 meter, so that the total surface amounts to about 
1950 e. m?. and the volume to about 240 c. c. 
For 1 degree increase of temperature the volume will increase by 
0.235 c.c. and this causes in a tube of 2.5 m.m. bore, such as 
used by me, a displacement of 47 m.m.*). By means of the xylene 
a mercury column must be forced up, which will produce the regn- 
lation of the gas. As the mercury may not come into contact with 
the copper we have soldered on to the end of the spiral ¢ (see the 
fig. to the left) a flanged tube j, provided with a screw thread and 
with a groove of 2 m.m. depth into which the glass tube & fits 
easily. The rest of the groove is filled with some cork rings. Round 
the glass tube, ground flat at the end, I have sealed a long flanged- 
tube 7 with a smooth rim and over this a loose nut m fits into the 
screw thread of the tube 7. If the nut is screwed up the glass tube 
compresses the cork packing and the closure is perfectly tight, and 
the xylene does not wet the sealing-wax. Unto the glass tube 4 is 
sealed the reservoir » and to this a narrow bent glass tube and 
reservoir 0 while above this the narrow tube p of 2.5 m.m. bore 
projects beyond the heating bath and there joins the wide tube g. 
1) Bose, Leistungsfähigkeit und Konstruktionsprinzipien von Präzisionsthermostaten 
mit selbstthätiger Reguliering. Mech.-Zeit. 1899, 
2) Smrrs, Manostat. Zeitschr. für phys. Chem. 33, p. 39, 1900. 
3) TRauBE und PrincussonN, Ein einfacher Thermostat und Druckregulator. Mech. 
Zeit. 1897. 
*) If the temperature remains constant displacement of 1 m. m. is brought about 
by a variation of 22 c.m. of mercury pressure. 
3 
Proceedings Royal Acad. Amsterdam. Vol. IV. 
