-2©2 Mr* Walker’s 'Experiments on the 
Exp. 2. On December 30. three ounces of a mixture com- 
pofed of ftrong fuming nitrous acid two parts, and ftrong 
vitriolic acid and water each one part, were cooled in a half 
pint tumbler immerfed in a frigorific mixture, till the tempe- 
rature of the diluted mixture of acids was reduced to — 30°. 
The tumbler was then removed out of the mixture, and 
vitriolated natron (Glauber’s fait) in very fine powder, pre- 
vioufty cooled to — 14 0 by a frigorific mixture, added by degrees 
to the liquor in the tumbler, ftirring it together until the mer- 
cury in the thermometer funk to — 54 0 . The hydrometer 
■ufed in the former experiment, with its lower bulb three- 
fourths full of mercury, was now immerfed and ftirred about 
in the mixture for a few minutes, when on taking it out, and 
inverting it, I had the fatisfaftion to find the fame proof of 
the mercury being frozen as in the former inftance. It was 
immediately (hewn to the gentlemen prefent, who exprefled 
likewife their entire fatisfa&ion. Nearly four ounces of the 
powdered fait was added ; but, I believe, fome was added after 
the greateft effect was produced. I had no nitrated ammonia 
by me, otherwife I (hould have ufed upon this occafion, inftead 
of vitriolated natron alone, a mixture of thefe two falts in 
powder, in the proportion of feven parts of the former to 
eight of the latter. The temperature of the room in which 
thefe experiments were made was -f 30° each time, and the 
mercury taken from ajar containing feveral pounds. 
Exp. 3. By an experiment made purpofely on January 10. 
laft, at which Dr. Bourne was prefent, I have found that 
mercury may be congealed tolerably hard, by adding frefh. 
fallen fnow, at the temperature of + 32% to ftrong fuming 
nitrous acid, previoufly cooled to between — 25° and — 30% 
which may be very eafily and quickly effected by immerfing 
6 the 
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