CHEMISTRY. .389 
foTced to Sffue from the globe by another pipe fixed in 
the ftopper cf the orifice, and communicating with the 
pneumatic ciftern, as at A, fig. 3. 
This procefs is exafitly the inverfe of that which I pro- 
pofed in my work on aeroftatien, to fill a balloon of in¬ 
flexible matter with hydrogen gas. ft was founded on 
the fame principle, the difference of the fpecific gravity of 
the two fluids. Here'it had the advantage of leaving the 
veffel perfectly clean ; an important condition, and which 
it is fo difficult to obtain when air is expelled by mercury. 
; It was yeadily forefeen that the fir It portions of the 
oxygen gas would become mixed with the atmofpheric 
air, and that it would be neceflary to difplace this mix¬ 
ture feveral times by new quantities of oxygen gas, 
that no more azotic gas might remain in it, or, at leaft, 
that the remaining quantity fhould be fo fmall as to be 
incapable of having a fenfible effe£V on the refults of the 
experiment. We had even contrived means to determine 
it, by receiving under the pneumatic jar the laft por¬ 
tions difplacea, that we might fubjefit them to a eudio- 
metric proof. With this view we employed eighteen de¬ 
cagrammes (about fix ounce?) of the oxygenated muriat 
of potaffi, which were put into a retort, at once to fur- 
nifti, at one operation, the whole quantity of the gas ne~ 
ceffary for this renewal. Thofe who have not tried this 
method of fubftituting one aeriform fluid for another, 
might entertain fiome doubt refpe&ing the purity of that 
employed in our experiment; but it will be eafy for me 
to remove it. This was an article of fo much importance 
that we could not negleft attempting to collect proofs 
of it. 
We know with what fuccefs M. Humboldt applied to 
the improvement of eudiometry. The intereft which he 
took in our experiment induced me to invite him to come 
and determine himfelf with thofe inltruments, and by 
thofe proceffes, which were familiar to him, the purity 
of the oxygen gas in which the combultion was to take 
place. He readily accepted my invitation, as I had rea- 
fon to expefit, from his well-known zeal for the progrefs 
of fcience; and this article of our report is the produc¬ 
tion of his pen. I had likewife the fatisfafition of feeing 
him apply eudiometric inltruments to the examination of 
the reliduum of the gas after the combuftion. The fol¬ 
lowing is the refult of the proofs to which he fubje&ed 
that introduced into the apparatus to ferve for the com¬ 
buftion : 
Nitrous gas, difengaged, by means of copper, from 
weak nitric acid, was tried with fulphat of iron and oxy¬ 
genated muriatic acid, which fliewed in it from 0-09 to 
o-io of azot. One hundred parts of oxygen gas received, 
towards the middle of the operation, as it iifued from the 
globe,- in which we had propoled to difplace, in l'uccef- 
fion, common air by oxygen gas, were mixed with 300 
parts of this nitrous gas : there was an aeriform refiduum 
of o-66 : making allowance for 0-27 or 0-30 of azot, pre- 
exifting in the nitrous gas, we judged that, in 100 parts 
of gas tried, there were ftill thirty-fix of azotiq gas. We 
then continued to introduce into the globe frelh oxygen 
gas. We collected towards the end a portion which was 
fubjefited to the fame proof, in the fame proportions, with 
the fame nitrous gas. The refiduum this time was only 
thirty parts j and as the 300 of nitrous gas employed con¬ 
tained nine or ten parts for § of azot, we concluded that 
this oxygen gas was quite pure. Thefe are the words of 
M. Humboldt. 
When this firft condition was fulfilled, the queftion 
tlien was to place, in the center of this globe, the dia¬ 
mond deftined for the experiment. We had previoufly 
formed a fmall cup of the lower portion of a furnace- 
pipe, the tube of which, five centimeters in length, was 
fixed to an iron ftalk, and this ftalk was ftuck into a cy¬ 
linder of cork deftined to be inferted in the neck of the 
balloon. This cork was dipped in maftic to (hut its pores, 
and a fmall glafs tube palled through it to eftablilh a 
communication between the infide of the balloon and the 
Vol. IV. No. 205. 
mercurial ciftern, as (hewn at fig. 3. We then placed the 
diamond on the cup, where we left it, having put it there 
by means of a ribbon, which we drew from under it in 
an inftant, as foon as the balloon, or globe, had been in¬ 
verted, and its neck immerfed in the mercury. The bal¬ 
loon, in this pofition, was made fait in a kind of collet, 
which refted on the edges of an iron mortar that flawed 
as a mercurial pneumatic ciftern. We then exhaufted, 
by fnftion, a portion of the oxygen gas, fufficient to 
make the mercury rife to twelve centimeters above the 
orifice of the balloon. The diamond was the fame that 
had been already expofed to the aftion of the folar fire 
towards the end of the experiment of the preceding year, 
and which had loft only two decimilligrammes, and cou- 
fequently weighed 199-9 milligrammes, 3766 grains. 
On the 5th Fruflidor laft year, at one in the afternoon, 
we began to throw upon the diamond the focus of the 
large lens of the National Inftitute. The thermometer, 
expofed to the fun under a bell-glafs, indicated 39-75: 
the mercury in the barometer flood at 75-89 centimeters, 
twenty-eight inches 0-5 lines. The volume of air, in- 
doled by means of the mercury in the tub, brought to 
the preffure of 757-7 millimeters (twenty-eight inches,) 
and to the mean temperature of 12-5 degrees of the deci¬ 
mal thermometer, according to the experiments of Pneier, 
and the tables of Prony, was then found to be 11,470 cu¬ 
bic centimeters. 
Having taken the neceflary precautions to heat gra¬ 
dually the balloon, the point of the luminous cone being 
almolt in the center, we were obliged to cover with a 
glafs-plate the wooden fupporter, which w r as already on 
fire. The diamond firft exhibited a black point at the 
angle immediately ftruck by the fun. We afterwards 
faw it entirely black, and, as it were, charred : we dif- 
tinftly perceived, a moment after, brilliant points in a 
ftate of ebullition, as it were, on the black ground. The 
folar rays, having been for a moment intercepted, it ap¬ 
peared tranfparently red. The fun becoming obfcured 
by a cloud, we faw it of a much purer white than it had 
been at the commencement of the operation. The fun 
having now emerged from the cloud, the furface of the 
diamond affumed the appearance of metallic fplendour: 
it was then fenfibly diminifhed, and there remained no 
more than a quarter, of a lengthened form, without an¬ 
gles or perceptible edges, but ftill very white, and of a 
beautiful tranfparency. We obferved a flight fiffure at 
the bottom of the pipe which fupported it, but without 
any feparation of the parts. I mull not forget, that at 
the commencement of the combuftion, we thought we 
obferved a purpurefcent cone arifing from the fupport in 
the pencil of the folar rays; but this phenomenon was 
only an optical effetft, which depended on the pofition of 
the obfer.ver. 
The whole apparatus was left in the fame ftate, only 
defended by an inverted box placed over it, until the 7th, 
when we again bega'n, at one hour twenty minutes, to 
prefent the diamond to the focus. We foon obferved the 
fame phenomena as on the 5th, the black furface, the 
brilliant points in ebullition, which vanifhed and re-ap¬ 
peared according to the intenlity of the focus : we faw 
alfo a brilliant metallic appearance, or rather leaden-co¬ 
lour. This is the expreflion which the affiftants employed 
to charafterife this phenomenon. At one hour forty mi¬ 
nutes the diamond was entirely confumed. We at firft 
fufpe£ted that there ftill remained a brilliant particle ; 
but we foon judged that it was a vitrified point of the 
fupport, which was confirmed on infpedting the pipe 
when drawn from the globe. The queftion now was to 
collefit the produfts of the combuftion. No means feemed 
likely to be attended with more certainty, than to intro¬ 
duce water of barytes into the apparatus, taking care to 
adhere, as nearly as poffible, to the proportions indicated 
for the faturation of the carbonic acid, which we lhppofed 
muft have been formed, to prevent the uncertainty which 
the excefs of this re-agent might occafion in the refults. 
5 G The 
