132 
in Figures 16 and 17 as well as the hydrogen generator and wash- 
bottles were kept on 27°. Constancy of temperature within 4 of a 
a 
Og ——— 
Fig. 18. 
degree throughout the whole thermostat, which is amply sufficient, 
was attained by electrical heating in the following way. 
Under the perforated bottom A, like the side walls and cover of 
the thermostat made of ‘‘eternite’, a kind of concrete, some 130 
metres of constantan wire of 0.4 m.m. diameter are spread out on 
a light frame. The current from the main of 220 Volts can be 
admitted to this wire by the relay Zi, an electrotechnical arrange- 
ment obtainable everywhere. A shunt of the current is reduced to 
some 8 Volts in the transformer 7. This reduced current runs 
through the electromagnet £/ and is broken or opened by the 
regulator C. The latter is of the type, described by CraRkK *), a spiral 
of nickel seeuring contact always at the same point of the mercury 
meniscus in a 2 m.m. wide capillary in pure hydrogen. To reduce 
sparking the poles of this regulator are also connected with a 
small condensor. 
1) J. Amer. Chem. Soc. 1913, 35, 1889. 
