905 
by melting them together in iridiumfree platinum-crucibles. The 
crystallised products are in most cases slightly pink or pale blue 
tinged by metal extracted from the walls of the crucibles: We used 
in the synthesis ‘also ZnCO,, but with less result. Analysis of the 
products proved, that originally too much S/O, was present; but 
the evaporation of the ZnO appeared however to be only very 
slight, if the crucible was covered ©. After several improvements, 
we obtained a product, whose analysis gave: 
Observed: Calculated: 
ZnO 42.43°), 42.24 °/, 45de 
m0; OTS O Ae 9108 Deo 
The obtained, stainless white substance could thus be considered 
to be pure ZnS/O,. With thermoelement IL the E.M.F. at the melt- 
ing-temperature was determined to be: 
14786 M.V., with a furnace-gradient of 75 M.V. per minute. 
14804 MV, „ „ ut ze (ONE 2 
14780 MV, ,, „ 5 OMV 5 D 
Mean: 14799 M.V. +12 M.V. (uncorr.). 
The correction of this thermoelement being at this temperature 
about —10 M.V., the reduced E.M. F. can be fixed upon 14789 M.V. 
+12 M.V., corresponding with a meltingpoint of 1437° + 1° C. 
According to Strm*) the meltingpoint is: 1429° C.; according to 
van Kroosrer®): 1419° C., but in both eases the experiments were 
made in the accustomed way. In cooling-experiments a solidifying- 
point was observed beneath 13700 M.V.; nor did we get any 
positive result in experiments, where the strongly heated substance 
was suddenly quenched in cold mercury, because in the quenching- 
product there were always crystals found besides the glassy substance. 
The solidified mass is weakly birefringent and has often a porcelain- 
like aspect, the grains of it being thus only transparent at the 
extreme borders. Evidently the product consists of very complicated 
parallel aggregations of thin, felty needles. The refractive indices 
were: n, = 1.623 + 0.006, and n, = 1.616 + 0.006, the birefringence 
thus being 0.007. The determination of the indices is very troublesome ; 
for the glass we found a mean value of 1.650. The specific gravity 
of the erystallised ZnSiO, at 25° C. is: dy = 3,52. 
1) Using ZnO; instead of ZnO with the synthesis, the loss of ZnO by flying 
away, appears to be much more appreciable. 
2) Srei, Z. f. Anorg, Chem. 55. 165. (1907). 
3) Van Kroosrer, Z. f. Anorg. Chem. 69. 135. (1910). 
