1811.J } 
sent themselves under a view entirely 
hew. A revolution in many «parts of 
chetnical philosophy is at hand, and per 
haps it will -be found’ that the progress of 
snowledge is not sufficiently advanced 
to expect the permanent establishment 
of any system of chetnistry, which, like 
that of astronomy, will derive additional 
confirmation from the observations of 
€ach sicceeding age. We ought not, 
however, to suffer the brilliancy of Dr. 
Davy’s discoveries to impose upon our 
judgment; it is desirable that his con» 
‘clusions should be examined: with the 
Same freedom, and the same candour, 
with which he has opposed preceding 
theorves. It is our intention in the fole 
towing Numbers of our Magazine, to pre- 
Sent our readers with a general view of 
this experiments ‘and discoveries, that 
bear immediately upon received systems 
‘of philosophy, in which we shall include 
those he is announcing in his present 
Jectures at the Royal Institution. We 
shall in this Number advert tosome new 
Opinions, which, if established, are of 
Considerable importance in préttical 
chemistry, and other branches of datural 
philosophy. In his second lectue he 
Stated, that he had by decisive experi» 
ments proved the doctrines of Berthollet 
respecting chemical ‘affinity to -be erro. 
héous, Bergman, and former chemists, 
who had treated on this subject, had 
‘always supposed thar two substances 
which combine with a powerful chemical 
affinity for each other, could ‘not be 
separated from ‘this combination by a 
' third substance, which. had-a weaker 
affinity to either of them, whatever quans 
tity of the third’substance be employed 
in the experiment.» This was the unis 
versally-established opinion, till the cet 
lebrated Berthollet, by a variety of exs 
periments, which were admitted ‘as con 
clasive, made it appear ‘that the’ most 
powerful combinations might be decom- 
pounded by ‘substances with “weaker 
chemical affinities. « This doctrine is 
advanced in his “ Chemical Statics,” and 
his ““ Researches respecting Chemical 
Affinity,” and this Jaw ¢stabtished. 
“In comparing the affinities of two bo.» 
dies for a third, a weaker-uffinity in one 
bf the two, will be compensated by in- 
creasing the quantity.” Tt “was muchi 
easier to admit the authority of Berthol- 
let, than-to repeat and vary his expe- 
riments; his doctrine was generally res 
ceived, and chemistry was degraded from 
the cank of 4 science, ‘to a mere cullec- 
Proceedings of Learned Societiess 
157 
tion of insulated facts. Por, were this 
doctrine true, uncertainty must. attend 
all the operations of chemistry, and the 
powers and. laws of chemical aflinity 
could never admit of being numerically 
expressed, or become the subject of -cal+ 
culation. Dr. Davy stated, that, in ald 
the cases where two substances were 
separated from. their combinations by a 
third, having a weaker affinity, the expe- 
wiment had not been accurately made. 
The sglphat of barytes, or - barytes 
united with the sulphurie acid, for which. 
it has .agreater affinity, than any known 
substance, had been separated from its 
‘combination by potass; but Dr. DB. as- 
serted, that when ‘this had been done, it 
had been done by double affinity; the 
carbonic acid of the potass uniting with 
the barytes, and the sulpharic with the 
potasss When pure potass .was used, 
and the experiment was made in vacuoy 
‘no decomposition of the sulphat of 
barytes was effected, whatever propor- 
tion of potass might be used in the exe 
periments. In all the other cases which 
the had repeated, the decomposition of 
ithe substances \having mote powerful 
affinities by weaker ones, had been cases 
of double affinity in some instances, the 
water of sulution had itself formed a part 
ofone'ofthenew campounds. . , 
Every practical chemist will be dee 
Sirous ‘to see a full detail of these:expe- 
riments, by Dr. Davy. . Hewill also be 
anxious ‘to know how. Dr. Davy will ex- 
plain those eases of double elective 
affinities, in which the quantities em- 
ployed appear materially to affect the 
pesults. It is:stated, by Dr. Henry,.that, 
if one part of common-salt,be mixed in 
amortar with half its.weight-of red oxyd 
of lead, and-made into.a paste with 
water, no decomposition takes place after 
twenty-four hours, ‘Increase the weight 
of the oxyd of lead to three or four times 
that of the salt, and a decomposition of 
the salt will be effected. Before it can 
be admitted that the quantity, or mass, 
has no effect on chemical affinities, it 
remains to be proved, that in cases 6f 
double, as well.as of single, elective afli- 
nities, the intrease of quantity has no 
effect on the result, farther than satura- 
ting a greater or smaller quantity of one 
of the substances decompounded. 
The peculiar views of Dr. Davy re. 
specting animal-heat, will be the subject 
of future remark. In the present Nume 
ber, we shall notice those opinions on 
this subject, which he delivered this year 
1 in 
