899 
insignificant trace of iron. The quartz was of American origin, and 
may be considered to be almost 100 °/, SvO,. 
The finely powdered and well mixed materials were several times 
heated in- the platinum-resistance-furnace in iridium-free platinum- 
crucibles, and then melted in the FLErcHer-furnace. 
Then they were ground and sieved, and these manipulations were 
repeated, as commonly, three or four times. Notwithstanding all 
care, an analysis of the products proved, that the composition again 
differed from the theoretical one. Thus the calculated quantity of 
carbonate or silica was added, and all mentioned manipulations were 
again repeated several times. If analysis showed the composition of 
the finely ground product not yet to be the true one, the deficient 
quantity of one of the components was again added, ete. If by at 
least two analyses it was proved, that the product showed the right 
composition, it was used for the final determinations. To study the 
influence of a slight excess of one of the components on the melting- 
point, we investigated also in some cases a not yet quite pure 
preparation. 
All. thus. prepared compounds of Ba, Sr, Be, Zn and Cd were 
stainlessly white, and beautifully crystallised; only in the preparing 
of the zinc-salts sometimes a slight bluish or pink tinge was observed, 
evidently caused by the introduction of a trace of platinum from the 
walls of the crucibles; in the case of the pink manganese-compounds 
a partial brown colouring appeared to be unavoidable in the repeated 
heatings. 
§ 4. Strontium-metasilicate. A preparation of SrSiO0,, whose 
analysis gave the following numbers : 
Observed : Calculated : 
SiO, 759°’, 37,70", 36,78°/, 
SrO 62,40°/,  62,35°/, 63,22°/, 
and which thus showed yet an excess of 0,87°/, Si0,, was first 
used for the meltingpoint-determinations. With thermo-element IL 
we found successively : 
16509 M.V., with a furnace-gradient of 30 M.V., per minute. 
16501 M.V., ,, 5, e joke hl (ee 
16495M.V., .,_,, : PAO MEV: LS 
16505 MV, .,, 5, : TOM Viel): 
mean.: 16502 M.V.. +7 M.V. (uncorr.). 
The. correction for this thermo-element at this temperature being 
