608 DE. A. DTTPEE AND F. J. M. PAGE ON THE SPECIFIC HEAT AND OTHEE 
Section V . — Bate of Expansion. 
The rate of expansion is determined by carefully estimating the specific gravity of the 
different mixtures, at the temperatures 10°, 15°‘5, and 20° C. 
The specific-gravity bottle employed is a rather large two-necked bottle of thin glass. 
In one of the necks a delicate thermometer is fixed, serving as a stopper ; the other neck 
ends in a capillary tube about 120 millims. long; 100 millims. from the upper end a 
mark is etched on the tube, and the capacity of the bottle, when filled up to this mark, 
is carefully measured. As it is difficult to fill such a bottle exactly up to the mark at a 
particular temperature, the level of the liquid in the capillary tube is only roughly 
adjusted, and the distance of the surface of the liquid from the mark accurately measured. 
It was found that 1 millim. of the tube contained 0'00195 cub. centim. ; this being 
known, the quantity of liquid contained in the tube above the mark could be calcu- 
lated, and its weight subtracted from that found, in order to get the weight of the 
contents of the flask when filled up to the mark. 
The thermometer is carefully ground in to fit the neck of the flask ; it has a long thin 
bulb passing through almost the entire depth of the specific-gravity bottle. Its range 
was from 8° to 25° C., divided into twentieths of a degree ; and with a telescope -^o 
degree Centigrade could be read off. 
The specific-gravity bottle is placed in a water-bath, surrounded by a double cylinder 
of tin plate. 
The temperature of this water-bath is under perfect control by means of the following 
arrangement. 
The water-bath contains a coil of metal tube like an 
ordinary condenser. The lower end of this coil is con- 
nected with a second and smaller worm, which is 
contained in a small water-bath. The latter is heated by 
a lamp and kept gently boiling. The lower end of this 
second worm is bent upwards, and terminates in a long 
funnel. Any water poured into this funnel will pass, first 
through the worm, surrounded by boiling water, and be 
thus heated, and then through the tube in the water- 
bath containing the specific-gravity bottle, when it will 
give up its heat and raise the temperature of the water- 
bath. By regulating the flow of water, the temperature 
of this water-bath can be raised quickly, or kept constant 
at any desired point ; so that with a little care the tempe- 
rature can be raised in a few minutes from 10° to 20°, and kept within ^ of a degree of 
the latter temperature for any length of time. To ensure a uniform temperature, the 
water is constantly agitated by the passage of a rapid current of air from below upwards. 
The temperature of the bath is taken by a thermometer exactly similar to the one 
inside the specific-gravity bottle. 
Fig. 4. 
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