900 
— 26 M.V., the melting-point can thus be fixed at 16476 M.V. + 7 M.V., 
this being: 1577,°5 + 0,5 C. on the nitrogen-gasthermometer. 
This compound erystallises perfectly, although perhaps not so 
extraordinarily rapidly as the barium-silicate. In cooling-experiments, 
where the molten mass was shaken continually by oscillations 
produced by repeatedly tapping and knocking the Marquarpt-tube, 
even with a gradient of 3°,5 or 5°C. per minute, the liquid could be 
undercooled down to 1239° C., a spontaneous crystallisation afterwards 
occurring, in which the temperature rose to 1339° C. because of the 
relatively great heat-effect. In another experiment undercooling was 
produced to about 1264°C. in this way, a rise of temperature there- 
upon being observed after crystallisation, up to 1547° C. Two refractive 
indices of the solidified substance were measured: n, = 1,595 
+ 0.001, and n, = 1,625 + 0,001. 
Now the preparation was improved by addition of the calculated 
amount of SrCUO,, the mixture repeatedly heated and melted, and 
again several times analysed. The data obtained were now: 
Observed : calculated : 
SiO, 36,4°/,  36.5°/, oe 436,789), 
SrO 63,6°/,  63,5°/, 63,22°/, 
The deviation’ from the theoretical composition is only about 
0,3°/,; the influence on the meltingpoint appeared to be without 
significance. 
In the usual way we now determined the melting-point of this 
beautifully crystallised, irreproachably white product; with the same 
element /// we found successively the following values for the 
E.M.F. of it at the meltingpoint: 
16515 M.V., with a furnace-gradient of 45 M.V, per minute. 
16496 MEV... nnen ‘ OMEN 
AGSOU MEV, SE 5 oy 00 EWG oe, 
Mean: 16504 M.V., +10 M.V. (uncorr.) a 
LE) 
», 
After correction (—-26M.V.), the true melting-temperature may 
thus be fixed at 16478 M.V. +10 M.V., this corresponding with: 
1578°C. +1°. An excess of 0,9°/, (weight proc.) of Si0, seems 
to cause a lowering of the meltingpoint of about 1° C. 
On cooling the molten mass it was observed, that with undercooling 
to about 12200 M.V. and with continual tapping of the crucible, 
every solidifying-temperature between 1306° and 1364° C. could be 
found. So e.g. we cooled in one of the experiments with a velocity 
of 4,°5 per minute: the result was an undercooling to 1225° C., and 
