1807. ] 
scripuon of their external parts, and did 
hot endeavour to obtain a more intimate 
knowledge of their structure, by means 
of anatoiny and chemistry. 
_ _M. Fourcroy has published a new and 
enlarged edition of -his Philosophy of 
Chemistry, which M. Cuvier justly con- 
siders as the best elementary work on 
that science. 
Aitruction and repulsion. These two 
powerful agents in nature have, during 
the present year, as we learn from this Re- 
port, attracted the attention of philoso- 
phers. 
It is well known, that ice is lighter than 
water, since it swims in it. On the other 
hand, hot water is, in general, lighter 
than that which iscold. But does not this 
fluid become uniformly condensed, in 
proportion as it is cooled, and expand 
Suddenly at the moment of its congela- 
tion? ‘This, however, is not the case ; for 
water is at its maximum of density, when 
a few degrees above the freezing-point. 
This M. Febvre-Gineau proved by direct 
experiments, several years ago, by means 
pf the thermometer and hydrostatical ba- 
dance. Since that period, Count Rum- 
ford has, by weil devised experiments, 
rendered the facts still more evident.# 
M. Bertholiet perseveres with indefati- 
gable industry in his Chemical Rescar- 
ches, a continuation of which has ap- 
peared during the present year. 
He therein, proves that, by means of | 
pressure, we may combine, with the 
three alkalies, a much greater quantity 
of carbonic acid than usual, and thus 
form neutral salts, as well as with the 
other acids.” He restricts the use of the 
term carbonate to these combinations, 
while he gives to those usually formed 
with this acid and the alkalies, the name 
of sub-carbonates; and shews, that there 
are between these two many interme- 
diate states. 
The same holds equally true in 
the earthy carbonates, and many 
other salts, The phosphate of soda, for 
example, is cerystallizable, both with 
an excess of acid, and an excess of 
basis. The partizans of the old‘ doc- 
trines suppose that, in such cases, no 
combination takes“place, but, that the 
Superabundant principle remains mere- 
ly interposed in a free state, between 
the molecules of the two principles, com- 
Lined in the usual proportion. M. Ber- 
* An account o! these experiments will be 
found in vol, xxii, p. 474, of the Monthly 
Magazine. 
Proceedings of Learned Societies. 
591 
thollet alleges, in reply to this Opinion, 
that, if this were the case, the suiphuric 
acid poured on a sub-carbonate would 
immediately seize upon the uncombined 
alkaline molecules, previously to entering 
into union with those combined with the 
carbonic acid. Now, that is not the 
fact; for the smallest drop of the former 
acid instantaneously produces an effer- 
vescence, and extrication of the second, 
The acidulous sulphate of soda effloresces 
on exposure to the air: that is, it parts 
with its water of crystallization, which 
could not happen, were the sulphuric 
acid uncombined with it, since there is 
no substance that more ereedily attracts 
the moisture of the air than this acid. 
M. Berthollet has furnished us with 
the means of estimating the degree of 
acidity of the different acids, and the al- 
kalinity of the different bases, by the 
quantity which it is necessary to employ 
of each of these substances, completely 
to saturate or neutralize the other, su 
that no sign of any superabundant acid 
oralkaliis perceivablein the combination. 
He confirms this method by shewing, 
that the proportions of these quantities 
are umiform, and that if to one basis 
twice more of one kind of acid be ne- 
cessary tO saturate it, than to saturate 
another basis, the first will also require. 
twice more of any other kind of acid than 
the second. 
But the degree of resistance to heat 
does not correspond with this force, and 
it iS more easy, for example, to decom- 
pose by fire the carbonate of magnesia 
than that of lime, though the affinity of 
these two earths for the acid be nearl 
equal: the reason of which is, that the 
former carbonate contains much more 
water; and other experiments shew, that 
water favours the disengagement of car- 
bonic acid. 
The consequences deducible from 
these facts, in every branch of chemistry, 
and particularly in the theory of analyses, 
are incalculable. 
The tables of the affinities, anda great 
part of the analyses hitherto made; are 
iavalidated by them, and experience, in 
fact, proves 'that these data require to be. 
revised, Forexample, M. Klaproth, and 
afterwards M. Vauquelin, found a fifth 
of fluoric acid in the topaz, in which 
it was never before Suspected te 
exist. This stone must, therefore, be 
now transferred tu the class of substances © 
containing acids. 
Another mineral, hitherto considered 
#9 4 stone, is now found to he a metal, 
fe 
