364 On a New Metal, Pelopium, &e. 
exhibit with respect to their specific gravity. My experiments 
on this subject have led me to the most unexpected results; al- 
though I have not terminated my investigations, I will neverthe- 
less communicate at present some of the most important. 
Some time ago I drew attention to the fact, that in the artifi- 
cially prepared titanic acid the specific gravity gradually increases 
by long-continued ignition, until it attains that of rutile. In the 
same way the modifications of titanic acid which occur in na- 
ture, anatase and Brookite, may be converted by continued igni- 
tion into rutile. I thought that the publication of these facts 
would have induced chemists to examine the specific gravity of 
other oxyds at different temperatures, since these changes have 
an important influence on the atomic volume. ‘This, however, 
has not happened, with the exception of a very interesting inves- 
tigation of Count Schafgotsch, on the specific gravity of silicic 
acid, in which he has shown that opal, before heating to redness, 
has so low a specific gravity, that it floats on oil of vitriol; but 
that the specific gravity is so increased by heating to redness, that 
it equals that of chemically prepared silicic acid (2°2), but which 
is still considerably lighter than quartz and rock-crystal (2°6). 
_ The changes which the three metallic acids under considera- 
tion experience by heating to redness are far more remarkable. 
When the hydrate of pelopic acid is deprived of its water by a 
gentle red heat over a spirit-lamp, just sufficient to produce the 
phenomenon of incandescence, and then exposed to a strong Te 
heat ina charcoal fire, its specific gravity is considerably increased, 
If we examine the ignited acid under the microscope, we see 
that it consists for the greater part, of amorphous granules, 10 
which some small crystals are perceptible. The ignited acid was 
then exposed to the most intense, and at the same time continu- 
ous heat, that a platinum crucible is capable of bearing, that of 
the porcelain furnace of the Berlin Royal manufactory. The - 
acid was not melted by it, but was converted into a coarse sandy 
powder, which, examined under the microscope, consisted of 
perfect crystals. The specific gravity of the acid, however, 
was thereby considerably diminished; curious enough, it hi 
become still lower than that which the acid possessed after 
the hydrate had been exposed to a gentle heat over a spirit-lamp, 
in order to expel its water. 
On repeating this experiment, the specific gravity of the crys- 
tallized acid, which had been ignited in the porcelain furnace, 
was found to be constant, while by no other temperature co the 
acid be brought to a constant specific gravity. 
_ These experiments are in so far remarkable as they prove preé- 
cisely the contrary of what has hitherto been frequently admitted. 
Crystalline bodies, such as idocrase, epidote, and garnet, fuse at 
a high temperature, become amorphous, but of lower specific 
