246 BERZELIUS ON THE ALLOTROPY 
observed with the latter, and which characterizes this transition 
in several other bodies. When this modification of the oxide of 
chromium is crystallized, it scratches glass like crystallized silicic 
acid. It occurs in combinations, not only with sulphuric acid 
but also with several bases, and all these exhibit the same in- 
difference towards reagents in the moist way, both Crg as well 
as the oxide which has been heated to redness. We are ac~- 
quainted moreover with compounds of Crg with other bo- 
dies besides oxygen. H. Rose has shown that the chloride of 
chromium may be obtained in both conditions in the solid state. 
The aspect is the same ; but one is readily soluble in water, and 
readily decomposed by reagents, whilst the other is insoluble 
and resists the action of reagents at a low temperature. We 
have thus evidently a chloride of Cr., and one of Crg. 
But the oxide of chromium, in addition to the two isomeric 
states we have mentioned, assumes a third, viz. that in which it 
yields a blue hydrate, and red or violet salts with acids, from 
which, in the moist way, it passes into the state of green oxide, 
which yields green salts at a temperature even lower than 212° F. 
When its solution is concentrated, it passes in the course of time 
from green to red. Does this depend upon the existence of a 
third hitherto unknown allotropic condition of chromium, or 
upon other circumstances ? 
We have no ground for supposing chromium to exist in the 
state of Crg, either in chromic acid or in any of its compounds 
with bases with which we have hitherto become acquainted. 
Titanium exhibits exactly the same phenomena as chromium. 
The stability of the red crystalline titanic acid, formed at a high 
temperature, both by a red heat and the action of nitromuriatic 
acid, is well known. But titanium, reduced at a low tempera- 
ture from chloride of titanium by ammonia, by the method which 
H. Rose discovered, readily takes fire when heated, and burns 
vividly into titanic acid, is oxidized on being boiled with con- 
centrated nitric acid, and is dissolved by nitromuriatic acid. 
Titanic acid has its two corresponding isomeric modifications, 
and, like oxide of chromium, passes from the soluble into the in- 
soluble state with evolution of light. 
Tantalum, when reduced by potash and charcoal, does not 
exhibit any differences in its properties which allow of our sup- 
posing with any degree of certainty that it exists in several al- 
lotropic conditions. ‘That which has been reduced by charcoal 
