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694 COXE’S TRAVELS IN RUSSIA.
Fahrenheit, and that common mercury does not freeze with a lefs degree of cold than
pure mercury.
“* Fighth experiment.— February 1, 1785, a favourable cold of 15 degrees offering
this evening, we placed in the mixture fome revivified mercury, twice diftilled with
fixed alkali by Winterberger, a preparation which has been faid to refift a greater degree
of cold than the others ; but it froze in two and a half minutes, exactly at 32 degrees
of Reamur’s mercurial thermometer, in the firft glafs of cold mixture, and differed no
wile from all the other forts except the following.
“¢ Ninth experiment.—Mercury purified with ‘antimony froze in two different experi-
ments at 30 degracs with a fpirit thermometer, and in one with a mercurial thermo-
meter at 32 degrees, fo that there appears.a difpofition in this preparation to freeze with
a lefs ae of gold than the others; butit muft be remarked, that it has a blackith
dull colour and fluggifh motion.
“¢ Tenth experiment.—Mr, Coxe being curious to try the mallesbiity of mercury
diftilled with alkali, which has a bright and fluid eee aaes: I froze fome of it in atube,
at the fame time cooling the hammer in the refrigerant mixture, fo as to acquire the
fame temperature as the frozen mercury, defending the iron from the action of the ni-
trous acid by means of a glafs cylinder. This mercury bore feveral ftrokes of the cold
hammer, flattening like a leaden bullet.
*¢ Eleventh experiment.—I lattly froze fix drachms of common mercury, containing
twelve times as much tin foil asin experiment the fixth; but even this quantity of alloy
which rendered it almoft an amalgama, did not difpole it to freeze with lefs than 32 de-
grees of Reamur.
“February 16, O. S.—A cold of 24 degrees offering moft unexpettedly this morn-
ing, fo late in the feafon, and another experiment being fuggefted to me by an ingenious
friend, Mr. Romme, to put the point of congelation of pure mercury ftill in a clearer
light, I tried it about mid. day, when the cold was diminifhed 4 degrees in the fhade.
*¢ Mr. Romme remarked, that mercury takes up much more bifmuth than tin without
lofing its fluidity or colour, and as bifmuth is a metal oftener ufed to adulterate-it, and
difficult to be feparated, he thought a mixture of them was a proper fubject of experi-
ment to decide the queftion. I accordingly prepared an amalgama fo thick, that it fil-
vered glafs like a mirror by merely running over it, and adhered fo faft as not to be rew
moved without fcraping. But the freezing point of this very Impure mercury was the
fameas the others; viz. 32 degrees of Reaumur, bythe mercurial thermometer. The fpirit
thermometer being employed to try the cold of the frigorific mixture, to my furprize fell
no lower than the other thermometer inferted in the mercury contained as ufual in a tube,
“* Thus ended my experiments this feafon ; and I may venture to draw the following
inferences :
“The point of congelation of mercury is at 32 degrees below o on Reaumur.
“There appears no difference in the point of congelation of purified and common
mercury, except one preparation with antimony, which feems to congeal with a lefs de-
gree of cold than all the others.
“In fome circumftances mercury may be cooled below its freezing point, without
lofing its fluidity, even as far as 54 degrees, whilft the portion in which the bulb of the
thermometer is plunged, becomes folid.
‘© Thefe experiments do not affe& the credit of the mercurial thermometer, as an
accurate inftrument for meafuring the degrees of heat from the point of boiling water
to that of the congelation of mercury ; but no conclufions can be drawn from its mo-
tions below this point, as they depend on the contraction of the metal in a folid ftate
which
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