905 
Observed : Calculated 5 
SiO, 28,24°/, 28,19 °/, 28,22 °/, 
BaO 71,75°/, 71,85, 71,78 °/, 
The product could now indeed be considered as a chemically 
pure BaSiO,. The determination of the meltingpoint was now 
repeated, and gave with element III the following values: 
16823 M.V., with a furnace-gradient of 40 M.V. per minute 
16825 __,, ee = se er = 3 
16838 LE] ” ” LE] ” >» 45 9 ? Ad 
Mean: 16838 M.V. + 6 M.V. (uncorr.). 
The correction being here —26M.V., the meltingpoint of pure 
BaSiO, can thus be fixed at: 16803 M.V. + 6M.V., corresponding 
with 1604° + 0°5C. (G. Th.). An excess of 1,7 °/, weight proc. 
SiO, thus lowers the meltingpoint about 1° C. 
The specific gravity of the crystalline product appeared at 25°,1 C. 
to be d,.—=4.435. It erystallises on slow cooling of the molten 
mass in flat, small crystals, which only show a feeble birefringence : 
0.003 or 0.004; this is consequently 7 or 10 times smaller than in 
the case of the strontiumsalt. For the refractive indices we found : 
1.667 and 1.670, both numbers with deviations of about + 0.001 ; 
greater crystals often show an irregular extinction. 
To obtain a glass, the substance was heated to 1650° C. and 
then suddenly quenched in cold mercury. Notwithstanding all endeav- 
our, we did not succeed in changing the molten product into a 
glass, because of the exceedingly rapid crystallisation of the sub- 
stance. The melting-point is according to this so sharp, that BaSiO, 
may be recommended as a new substance for the calibration of 
thermoelements. 
After all attempts to get some information about a polymorphic 
transition with SrSvO, and Bosi, had been without success, we 
tried to obtain yet a second modification of these compounds by 
means of fluxes. For that purpose 0,5 gram of pure BaSiO, were 
mixed with 1 gram of sodium-wolframate, and in the same way 
0,5 gram of pure SrSiO, with 1 or 2 grams of the same salt, 
and then heated at 860° C. during 72 hours. Neither in these expe- 
riments, nor in others, where we started with SS:O,-glass, did we 
succeed in obtaining other crystals than those formerly obtained 
by the melting of the salts. 
Finally we wish to draw attention here also to theresults, which 
were obtained by means of the cooling-method, just because one 
would perhaps expect to find here in this favourable case some 
