BETWEEN THE FREEZING AND BOILING-POINTS. 
L53 
such as water, then E represents the difference of potential across a conducting wire 
passed through the tube in which the current C flows. 
We will deal entirely in this place with the method as applied to this latter case, 
such as a steady flow of water, and replace Js in the general equation by J, or the 
number of joules in one calorie. 
Let J = 4 ‘2 (1 8), where § is a small quantity varying with the thermal 
capacity of the water, then we may write the general equation, 
4-2 (1 ± §) Qt (0 1 - 0 O ) -f (0 1 - 0 O ) lit = EC*. 
Dividing through by t, and re-arranging the terms, we have 
4-2 Q {0 1 - 0 Q ) S + (0 l - 0 O ) h = EC - 4-2 Q (0, - 6 0 ). 
This we will call the general difference equation. 
The total heat-loss from the water will be made up of radiation from the surface ot 
the tube through which the water is flowing, conduction from the ends of the tubes 
containing the thermometers for measuring the temperature of the inflowing and 
outflowing water, and convection currents due to insufficient stirring around the 
thermometer bulbs. There will be a small gain in heat due to work done by 
the water in flowing through the fine tube. To study the effect of these upon 
the general difference equation it will be necessary to refer to the diagram of the 
continuous-flow electric calorimeter in its simplest form, given in fig. 1. 
A 
w 
1P- 
Fig. 1. Diagram of Calorimeter. 
y l 
In this AB represents the fine tube in which the water is heated while flowing- 
through, V, the vacuum-jacket, and C and P the inflow and outflow tubes connected 
to AB, in which the thermometers are placed. The water-jacket is shown at W, and 
includes the vacuum-jacket and inflow-tube C. The water enters the calorimeter at 
E from a reservoir separate from that supplying the water for the jacket, but 
maintained at the same temperature. The electric heating current passes through 
the fine tube AB through a platinum wire extending the whole length, but is 
arranged so as not to generate heat in the vicinity of the thermometer bulbs. The 
thermometer in C measures the temperature 6 0 of the inflowing water, and that in P 
VOL. CXCIX.—A. 
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