122 ROYAL SOCIETY OF CANADA 
ring, and a measured quantity of heat is introduced by means of a 
spiral of fine platinum wire immersed in the liquid and heated by a 
current of electricity of known strength. 
The calorimeter which has been thus far employed is made of 
nickel-plated copper, and is of cylindrical form, being four inches high 
and two inches in diameter. It is fitted with a cover having three 
holes, for the thermometer, stirrer and heating coil, to be described 
below. The size is unusually small, it having been thought desirable, 
among other things, to determine with how small a quantity of sub- 
stance accurate results could be obtained. It has been found that a 
calorimeter somewhat larger than the present one would be better. 
The spiral used for heating is made of one meter of pure platinum 
wire having a resistance of about six ohms, and wound on a frame made 
of mica. The ends of the wire are fused on to thick copper leads, 
whose free ends project some inches beyond the calorimeter, are bent 
over, and dip into two little mercury cups, thus connecting with the 
circuit outside. The current employed is obtained from six automobile 
accumulators of twenty-five ampere hours each, and is cut down by a 
resistance so that about 0-8 ampere passes through the heating spiral 
when it is in use. A Weston ammeter is inserted in series, and a 
Weston voltmeter is connected so as to give the drop of potential 
between the terminals of the heating spiral. A rocking mercury switch 
is so arranged that by its means the current can be turned through the 
heating spiral, or through an auxiliary resistance approximately equal 
to it. Before any determinations are made, the current is allowed to 
flow for a considerable time through this resistance in order that all 
connecting wires, joints, etc., may become warmed, and everything 
reach a steady state. 
The stirrer is shaped like the propeller of a steamer, is made of 
copper, and fixed by means of plaster of paris to the end of a narrow 
glass tube which projects through the cover of the calorimeter. This 
tube is connected at its upper end to the vertical shaft of a tiny pulley 
by a short piece of rubber tubing, and the pulley is revolved by an elec- 
tric fan motor to which it is connected by a belt. The speed of the 
motor is variable, that generally employed driving the stirrer at about 
680 revolutions per minute. The blades of the stirrer are just above 
the bottom of the calorimeter and are curved so as to lift the mixture 
of solid and liquid. 
The temperature is read on a mercurial thermometer (of Max 
Kaehler and Martini’s manufacture), specially made for calorimetric 
work, and divided to twentieths of a degree; it is observed by means of 
a telescope, and readings can be made to hundredths of a degree. 
