Art. LI.—An Instrument for roughly determining the Relative Thermometric Conductivities of Liquids.
[Read before the Philosophical Institute of Canterbury, 4th May, 1898.]
Two similar capsules of thin “glass” or metal are placed vertically, one over the other, with the bulb of an open-air thermometer between them. The two capsules and the bulb are enclosed in a cylinder of considerably larger diameter, the
capillary stem of the thermometer coming in a horizontal direction through the cylinder wall. Through the upper capsule the vapour of some boiling liquid, or, if more convenient, warm water at constant temperature, is passed;
while cold water circulates through the lower. The liquid to be experimented on fills the cylinder, and finds itself, therefore, between the two capsules. After a time, depending on the thermometric conductivity of the liquid, a state of constant flow is set up. To compare two liquids the time to reach the constant state for each is measured, and the thermometric conductivities are then inversely as the times.
Naturally the apparatus lays no claim to scientific accuracy; it enables one, however, quickly, and with fair success, to demonstrate the relative conductivities of any two liquids. If the stem of the open-air thermometer is of fairly true bore, the relation between the times necessary for any required rise of temperature, or between the times for successive equal increments, also allows of easy demonstration.