DR. WALTER WAHL: PHYSICO-CHEMICAL DETERMINATIONS 
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bomb. The details of construction of the pressure-bomb and the water-jacket are 
seen from fim 2. 
'J’he water-jacket is heated by means of two small gas-burners, which are regulated 
by a mercury-regulator of ordinary type. In some series of measurements electrical 
beating a platinum resistance coll has been used, and the regulator for the heating 
current was then electro-magnetic. The liquid in the bath was well stirred by a small 
turbine stirrer driven by an ordinary hot-air engine. 
Temperatures were measurefl by thermometers, divided into tenths of a degree, 
which have been compared with similarly graduated thermometers standardized at 
the “ Pliysikallsch-Technische Iteichsanstalt ” in Charlottenl)urg. 
3. The Optical Installatioji. 
(l) The Optical Bench .—The optical observations are made by means of an optical 
bench, each end of which is fitted witli a screw-adjusting gear, the whole resting on 
