1797:] 
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PROCEEDINGS OF LEARNED SOCIETIES. 
oe 
MEMOIRS PRESENTED IN THE NATIONAL INSTITUTE OF 
FRANCE, DURING THE FOURTH QUARTERLY SITTING, 
Held on the 15th of Nivofe; or the sth of January, 1797: 
CLASS OF PHYSICS, 
‘PHE fir labours prefented to the’clafs 
during the three months which have 
jaft elapfed, have had chemiftry tor their 
“object. : 
Focrcroy and VAUQUELIN pre- 
fented a memoir on the acidulous phof- 
phate of lime. ‘ Chemifts,”’ faid they, 
«« have long been aware of the difference 
between the phofphoric acid obtained by 
fulphuric acid from phofphate of lime, 
and that produced from the combuftion 
of phofphorus. The firft, when evapo- 
rated, aflumes the appearance of glitter- 
ing feales, does not attract the moifture 
from the atmofphere ; and when formed 
into glafs, lofes the greater part of its 
acidity, its folubility, and tendency to 
combination. The latter, on the con- 
trary, appears in white light flocks, 
and is very deliquefcent, is capable of 
being melted into glafs, but preferves its 
acidity, folubility, and tendency to com- 
bination. Thefe differences were attri- 
buted to afmall quantity of fulphate of 
lime contained in the firft acid; but as 
it exhibits the fame properties, whether 
it has been extracted from its earthy 
bafe, by the fulphuric or any other of 
the mineral acids, it is evident, that ful- 
phate of lime cannot be the fubftance 
with which itis united. That which 
gives it its peculiar charaéters, is a {mall 
proportion of Jie, which continues fo 
ftrongly combined with it, as not to be 
taken away by any other acid: on the 
addition of- an alcali. however, a white 
powder falls down, which is phofphate of 
lime. 
The fame chemifts propofe, in the 
making of phofphorus, to ufe no more 
than 46 or 37 parts of fulphuric acid, to 
100 of phofphate of lime; and, in order 
to cbtain all the phofphorus contained in 
the acidulous phofphate of lime, they 
recommend the addition of nitrate of 
jead, which caufes a decompofition of the 
falt, producing an infolube precipitate 
phofphate of lead; from which, by the 
affiftance of charcoal, the photphorus is 
xafily procured. 
Fourcroy and VAuQueELIN have 
been profecuting their iluftrious ex- 
periments on the properties of one of 
the moft interefting chemical agents—on 
the different phenomena which the ful- 
phureovs acid exhibits in the various 
combinations of which it is fufceptible. 
The refults of the whole of thefe expe- 
riments (when brought to a termination) 
are to be publifhed, which, by com- 
pieting the fcientific fyftem of a very. 
curious part of chemiftry, and furnifhing 
alfo a genuine hiftory of the acid, will 
excite our ardent wifhes to fee the other 
branches of this vaft {cience brought to 
fimilar perfeétion. 
Lamarck has inveftigated, de nowo, 
the general principles on which the 
re{pective theories of the fame fcience 
are founded. From feveral memoirs 
which he read to the clafs, it appears, 
that he has particularly examined the 
refult of the alterations which the effen- 
tial particles of compofite bodies are 
capable of fuftaining from nature, or 
from art. He has confidered the union, 
greater or lefs, of the fubftances of 
which thofe particles are formed, together 
with’ the different combinations of the 
fame, and, proceeding by a natural tran- 
fition to contemplate the colours of ob- 
jeéts, he has invented a graduated feale, 
which he calls a chromometer, on which 
may be afcertained, by methodical tables, 
2790 fhades, ab/olutely and invariably 
the fame, without refpect of time. or 
place. This difcovery will neceffarily 
lead to the acquifition of extenfive come 
parative inftruments, calculated to faci- 
litate the progrefs of natural hiftory, and 
every other fcience in which it is requi- 
fite that colours fhould be indicated with 
precifion. _ 
GIRTANNER, a celebrated German 
profeffor, conceived that fome modifica- 
tion was neceijary to be adopted relative 
to one of the principles in the modern 
theory of the French chemifts—-viz. that 
hydrogene gas is the radical of the muri- 
atic acid. WANMONS, of Bruffels, an 
affociate of the inftitute, has tranfmitted 
to the clafs, a feries of experiments on 
this head, made with the greateft accu- 
racy, which, by laying open the appear- 
ances which led GrRTANNER into an 
error, give additional confirmation to that 
prineiple in the French fyftem, which 
the German profeffor had called in quef- 
tlon. | 
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