898 
A meltingpoint of 1494° C. for BaSiQ, is also given by Voroskov, 
Ann. Instit. Polyt. St. Petersburg, 15. 421. (1911). 
ZnSiO,, prepared by melting together ZnO and Si0, in poreelain 
crucibles, is said to erystallise at 1429° C.; the glass of this silicate 
should possess a greater specific weight (3,86) than the crystals (8,42). 
Finally Svein gives as solidifying-temperature of Sr,SiO,: 1598° C. ; 
the specifie gravity being 3,84, and for the glass: 3,57. In the same 
way Zn,Si0, would crystallise at 1484° C., and show a specific 
weight of 3,7. 
About Ba,SiO0, it is only mentioned, that products soiled by 
carbon were obtained; no data about melting-temperature or proper- 
ties are given. Data about beryllium-silicates: BeSiO, and Be, SiO, are 
only few: Srrin mentions, that the meltingpoint of BeS¢O, was too 
high, to be determined by means of tne thermo-element. Above 2000° C. 
the substance becomes a thin liquid; the specific gravity of the 
crystalline product is given as 2,35. Be,SiO, has evidently a very 
high meltingpoint, and erystallises readily; more detailed data are 
absent. 
On the silicates of manganese an investigation is published by 
DorrinckeL?); he mentions the compounds MnSiO, and Mn,Si0,, 
and says, that they melt under partial decomposition. However for 
MnO, the composition of the molten mass can only differ slightly 
from that of the pure compound. The temperatures are related. as 
follows: for MnSiO,: 1215° C., and for Mn,SiO,: about 1323° C. 
setween the two compounds there would be a eutectic point at 1185° C. 
If we now consider, that the data given for SSO, differ 242° C., 
for BaSiO, 122° C. from each other with different authors; that 
in no case the influence of the heating in an atmosphere of carbon- 
monoxide on these products and on the thermo-elements was inves- 
tigated, and that always the unreliable cooling-method was used in 
the study of these silicates, — then a renewed study of the phe- 
nomena here oceurring can hardly be said to be superfluous. Some , 
few data about these substances, although vet incomplete, may 
therefore be given already in the following pages. 
$ 3. The pure silicates were prepared by repeatedly: heating and 
melting together the purest, finely powdered quartz, and: chemically 
pure SrCO, and BaCO, in the calculated quantities. The employed 
SrCO, was free from barium-oxide, the BaCO, free from strontium- 
oxide. Both substances appeared to have no other’ impurity than an 
1) F. DoerincKer, Die Metallurgie, 8. 201. (1911). 
