PROFESSOR KOPP ON THE SPECIFIC HEAT OF SOLID BODIES. 
85 
with water, is equivalent to x parts of water, if f is the weight of the liquid in it, y its 
specific heat, m the weight of the solid substance, M the weight of the water in a calo- 
rimeter, including the value in water of the immersed part of a thermometer and of the 
calorimeter, T the temperature to which the glass and its contents have been heated 
before immersion in water, and T' the temperature to which the glass sinks when im- 
mersed in the water, while the temperature of the latter rises from t to t', then the 
specific heat (sp. H.) of the solid substance is 
TT M(f—t) — [r+fy) . (T— T) 
P ‘ 11 m(T-T') 
In the sequel I shall discuss more specially the manner in which the individual mag- 
nitudes in this equation were determined : I will first give a description of the apparatus 
and method which I used*. 
The glass vessel in which the substance is confined (Plate XX. a in fig. 1) is a tube of 
glass, the bottom of an ordinary test-tube. In it fits, but not air-tight, a cork c, which 
is pressed between two small brass plates that are screwed to a wire b. The solid sub- 
stance to be investigated, in the form of thin cylinders, or in small pieces the size of a 
pea, along with a liquid of known specific heat, which does not dissolve it, are placed in 
the tube in such a manner that the liquid covers the solid substance, and that there is a 
space between the liquid and the cork when it is inserted. The glass, when the cork is 
fitted, may be suspended to the balance by the wire b. Three weighings (1) of the empty 
glass, (2) after introducing the solid substance, and (3) after introducing the liquid, give 
the weight of the solid substance (in) and of the liquid (f). 
The heating apparatus (fig. 1) serves to raise the temperature of the glass with its 
contents. The glass is dipped in a mercury-bath A near its upper edge, and retained 
by a holder E. The mercury-bath, which consists of a cylindrical glass vessel, is sus- 
pended by means of a triangle round the neck of the vessel in an oil-bath B, which 
stands on a tripod C, and can be heated by a spirit-lamp D. A thermometer fixed 
to the holder F, is also immersed in the mercury-bath. 
The flame of the spirit-lamp may be regulated so that the thermometer d indicates 
the same temperature for a long time $. If it may be assumed that the contents of the 
glass a have also risen to this temperature, then the wire b being firmly held in the 
right-hand by its hook, and the clamp of the holder E in the left, the glass a is rapidly 
removed from the heating vessel to the calorimeter H (fig. 2). This is almost the only 
part of the entire experiment which really requires much practice ; the transference of 
* All figures on tlie Plate are one-third of the natural size. 
f Fig 7 shows in section how the glass with its contents and the thermometer dip in the mercury- bath and 
this in the oil-hath. 
+ In order to obtain temperatures constant at about 50°, a spirit-lamp with a thin wick is used, and this is 
pressed in the sheath so that the alcohol-vapour above it burns with a very small flame. The position of the 
wick and the intensity of the flame may be conveniently regulated if the upper part of the wick is surrounded 
by a spiral of thin copper wire whose ends project from the sheath. 
