PEOEESSOE KOPP ON THE SPECIFIC HEAT OE SOLID BODIES. 
129 
IV. — Experiments with Water. Glass 1. Temperature of the Air 17 0, 8-18°-3. 
T. 
T'. 
t'. 
t. 
M. 
m. 
/• > 
X. 
sp. H. 
O 
O 
o 
o 
grms. 
grms. 
grm. 
grm. 
47-6 
19-7 
19-37 
15-72 
26-945 
5-02 
1-93 1-000 
0-651 
0-188 
47-9 
19-9 
19-57 
15-92 
26-95 
55 
55 55 
55 
0-186 
47-6 
20-0 
19-65 
16-03 
26-985 
55 
55 55 
55 
0-191 
47-3 
20-0 
19-67 
16-08 
26-98 
55 
1-915* „ 
0-196 
Mean . . . 0T90 
The average of these four means, 0T86, 0T87, 0T80, 0T90, gives 0T86 as the 
specific heat of quartz between 20° and 50°. 
It was interesting to determine also the specific heat of amorphous silicic acid. I ac- 
cordingly made experiments with opal and with hyalite, taking into account the water 
contained in these minerals. If the quantity of silica in the mineral taken is m , that 
of the water in it w, and z the specific heat of the water contained in the mineral, then, 
taking the other symbols in the sense hitherto assigned to them, the specific heat of 
the silica in the mineral can be calculated by the formula 
sp. H= 
M(t'—t) — (x+fy + wz) (T— T') 
m (T-T') 
But though the quantity of water contained in the (air-dried) minerals investigated 
is so small (scarcely exceeding 4 per cent.), the specific heat of silicic acid is found to 
be very different, according as (a) the specific heat z is put equal to 1, that of liquid 
water, (/3) or equal to 048, that of solid water or ice (which is at least correct for 
far the greater part of the water of these minerals, vide § 97). I give as follows, 
under a and (3, the numbers resulting from both calculations. 
Noble Opal from Honduras: yellowish, colourless in small pieces. The air-dried 
mineral contained 4-3 per cent, of water ; in the following experiments 4T2 grms. of 
opal were used, containing, therefore, 3- 943 grms. of anhydrous substances ( m ) and 
0T77 grm. of water (w). 
Experiments with Naphtha B. Glass 3. Temperature of the Air 18°-5-18°-7. 
T. T'. t'. t. M. m. w. f. y. x. sp. H. 
o o o o grms. grms. grm. grm. grm. a. (}. 
50- 4 20-6 20-34 18-10 26-98 3-943 0-177 1-69 0-419 0-453 0-175 0-198 
52-6 20-6 20-32 17-84 26-985 „ „ „ „ „ 0-191 0-214 
51- 9 20-6 20-32 17-92 26-98 „ „ „ „ „ 0-185 0-209 
51-3 20-6 20-32 17-96 26-955 „ „ 1-67* „ „ 0-188 0-211 
Mean . . . 0-185 0-208 
Hyalite from Steinheim near Hanau. Small limpid spheroidal masses. The air- 
dried mineral contained 3-65 per cent, of water. In the following experiments 3‘795 
* After drying the stopper. 
T 2 
