FREEZING. 
30 
that the mercury in his barometer was frozen. He haft- 
ened immediately to his houfe to behold fuch a fiirprifing 
phenomenon ; but though he was vvitnefs to the fact, ob- 
ferving that the mercury did not continue in one column, 
but was divided in different places as into little cylinders, 
which appeared frozen, yet the prejudice he had enter¬ 
tained againft the podibility of the congelation, would 
not allow liim to believe it. 
Another fet of obfervations, in thecourfe of which the 
mercury muft frequently have been congealed, were made 
by profelfor Gmelin at Kirenga fort, in 57^ north lat. and 
108 eaft Ion. his thermometer, at different times, fland- 
ing at —108, —86, —190, —113, and many other in¬ 
termediate degrees, in the courfeof the winter of 1737-8. 
On the 27th of November, after the thermometer had 
been flanding for two days at —46°, he found it funk at 
noon to—108. Sufpedfing fome miftake, after he had 
noted down the obfervation, he inflantly ran back, and 
found it at —102 ; but afcending with fuch rapidity, that 
in the fpace of half an hour it had rifen to —19°. This 
phenomenon, which appeared fo furprifing, doubtlefs 
depended on the expanfion of the mercury frozen in the 
bulb of the thermometer, and which now melting, forced 
upwards the fmall thread in the ftem. And firnilar ap¬ 
pearances were obferved on other days afterwards, when 
the thread of quickfilver in the thermometer was feparated 
iibout 6 degrees. A fecond inftance where a natural con¬ 
gelation of m.ercu'ry has certainly been obferved, is re. 
corded in the tranfactions of the royal academy of fciences 
at Stockholm, as made by Mr. Andrew Hellant. The 
weather, in January 1760, rvas remarkably cold in Lap- 
land ; fo that on the 5th of that month, tlie thermome¬ 
ters fell to—76,—128, or lower; on the 23d and follow'- 
ing days they fell to —58, —79, —92, and below —238 
entirely into the ball. This was obferved at four 
different places in Lapland, fituated between the 65thand 
78th degrees of north lat. and the 21ft and 28th degree of 
call longitude. 
But the congelation of quickfilver, by an artificial 
freezing mixture, was firfl: obferved, and put beyond 
doubt, by Mr. Jofeph Adam Braun, profelfor of philofo- 
phy at Peterlburg. This gentleman, wilhing to try how 
many degrees of cold he could produce, availed himfelf 
of a good opportunity which offered for that purpofe on 
the 14th of December 1759, w lien the mercury in the 
thermometer Hood in the natural cold at —34, which it is 
now known is only 5 or 6 degrees above its point of con¬ 
gelation. Afiilling this natural cold therefore with a 
mixture prepared of aquafortis and pounded ice, his 
thermometer was funk to —69. Part of the quickfilver 
muflnow have been really congealed, but unexpefted by 
him, and he only thought of purfuing his objedt of pro¬ 
ducing (fill greater degrees of cold ; and having expend¬ 
ed all his pounded ice, lie was obliged to ufe fnovv inftead 
of it. With this frefli mixture the mercury funk to 
—100, —240, and —350°. Taking the thermometer out, 
he found it whole, but the quickfilver fixed, and it conti- 
tiued fo for twelve minutes. On repeating the experi¬ 
ment, with another thermometer which had been gradu¬ 
ated no lower than —220, all the mercury I'unk into the 
ball, and became folid as beforCj and did not re-afeend 
till after a ftill longer interval of time. Mr. Braun now 
fufpedted that the qnicklilver was really frozen, and pre¬ 
pared for making a decili.ve experiment. TJiis was ac- 
compliihed on the 23th of the lame month, and the bulb 
of the tb.ermometer broken as foon as the metal was con¬ 
gealed ; when it appeared that the mercury was clianged 
into a I'olid and lliining metallic mafs, which flatted and 
extended under the tlrokes of a peltie, being rather lefs 
h ird tlian lead, gnd yielding a dull found like that metal. 
Mr. j^ipinus made firnilar experiments at the fame time, 
employing as well thermometers as tubes of a larger bore ; 
in which la(t he remarked, that the quickfilver fell fen- 
fibly on being frozen, afluming a concave furface, and 
likewife that the congealed pieces funk in fluid mercury ; 
alio, in their larther experiments, they invariably found 
2 
that the mercury funk lower when the whole of it was 
congealed, than if any part of it remained fluid : all ibew- 
ing that, contrary to water, rrcercury gontradfed in freez¬ 
ing. It was farther obferved, that the mercury when 
congealed looked like the mod: poliflied filver, and when 
beaten flat, it was eafily cut with a penknife, like foft 
thin 'heet lead. 
The fact being thus ertabliflied, and fluidity no longer 
to be confidered as an elTential property of quickfilv'er, 
Mr. Braun communicated an account of his experiments 
to the Peterfburg academy, on the 6th of September, 
1760; of which a large extract was inferred in the Phi- 
lofophical Tranfadtions, vol. Hi. p. 156. He afterwards 
declared that lie never fuftered a winter to pafs without 
repeating the experiment of freezing quickfilver, and 
never failed of fuccefs wlien the natural cold was of a 
fufficient ftrength for the purpofe; and this degree of 
natural cold he fuppofes at —10 of Fahrenheit; thougli 
fome commencement of the congelation might be per¬ 
ceived when the temperature of the air was as higli as -f 2. 
The rel'ults of all his experiments were, that with the 
abovementioned frigorific mixtures, and once with redli- 
fied fpirits and fiiow, when the natural cold was at_28° 
he congealed the quickfilver, and difeovered that it is a 
real metal that melts with a very fmall degree of heat. 
However, not perceiving the necelfary confequence of its 
great contradfion in freezing, lie always confounded its 
point of congelation with that of its greateft contradfion 
in freezing, and thus marked the former a great deal tocr 
low. In the procefs of his obfervations, Mr. Braun 
found that double aquafortis was more effectual than fpirit 
of nitre; but with this fimple fpirit, which feldom brings 
the mercury lower than —148, this metal may, be frozen 
in the following manner: fix glafles being filled with 
fnow as ufual, and the thermometer put in one of them, 
tlie fpirit of nitre was poured upon it; when the mer¬ 
cury would fall no lower in this, the thermometer was 
removed to the fecond, and fo on to the third and fourth 
in which fourth immerfion the mercury was congealed. * 
Mr. a^spinus gives the following diredtion for ufino-the 
fuming fpirit of nitre: Take fome of this fpirit, cooled- 
as much as poflible, and put it into a wine glafs till it be 
about half full, filling it up with fnow, and (lirring them 
till the mixture become of the confidence of pap ; by 
which means you obtain, almod in an indant, the necef- 
fai'y degree of cold for ihe freezing of quickfilver. 
It is remarked by Mr. Braun, that by the mixture of 
fnow and fpirit of nitre, which froze the mercury, he ne¬ 
ver was able to bring thermometers, filled with the molt 
highly redtified fpirit of wine, lower than —148 ; fo that 
the cold vvliich will freeze mercury, will not freezej'pirit 
of wine ; and therefore fpirit thermometers are the mod: 
fit to determine the degree of coldncfs-in frigorific mix¬ 
tures, till we can condrudl: folid metallic thermometers 
with fufficient accuracy. Mr. Braun tried the eflecls of 
difl'erent fluids in his frigorific mixtures : lie always found 
that Glauber’s fpirit of nitre and double aquafortis were 
the mod powerful; and from a number of experiments 
made when tlie temperature of the air was betw'een 2r 
and 28 of Fahrenheit, he concludes, that fpirit of fait 
pounded upon fnow increafed the natural cold 36°; fpirit 
of fal ammoniac, 12 ; oil of vitriol, 42 ; Glauber’s f pirit 
of nitre, 70; aquafortis, 48; fmiple f pirit of nitre, 36 j 
dulcified fpirit of vitriol, 24; Hoffman’s anodyne liquor, 
38; fpirit of hartfnorn, 12; fpirit of fulpliur, J2; fpirit 
of wine rectified, 24; camphorated fpirit, i8; French 
brandy, 14; and feveral kinds of wine increafed the na- 
turalcold to 7, 8, or 9, degrees. 
The mod remarkable freezing of mercury by natural 
cold, was that rejated by Dr. Peter Simon Pallas, whq had 
been fent by the emprefs of Ruffia, with fome other gen- 
tlemeii, on an expedition firnilar to that of Mr. Gmelin. 
Being at Krafnoyarfk in 1772, in north lat. 56° 30', and 
eaft Ion. 93°, he liad an opportunity of obferving the' 
phenomenon very accurately. On the 6th and 7th of 
December that year, fays he, there happened the greateft 
cold 
