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XIII. fuppofed Effedi of boiling upon JVater, in difpojing 
it to freeze more readily^ afcertained by Experhnents. 
By Jofeph Black, M. D. Profeffor of Chemijiry at Edin- 
burgh, in a Letter to *S’/r John Pringle, Bart, P, R. S, 
TO SIR JOHN PRINGLE, BART. P. R. S. 
DEAR SIR, Edinburgh, Feb. ii, 1775. 
Reclde, Feb. TT TE had lately one day of a calm and 
1775* VV clear froft; and I immediately feized 
the opportunity, which I miffed before, to make fome 
experiments relative to the freezing of boiled water, in 
comparifon with that of water not boiled. I ordered 
fome water to be boiled in the tea kettle four hours. I 
then filled with it a Florentine flafk, and immediately 
apply ed fnow to the flafk until I cooled it to 48° of 
FAHRENHEIT, the temperature of fome unboiled water 
which flood in my fludy in a bottle ; then putting four 
ounces of boiled, and four of the unboiled water, fepa- 
rately, into two equal tea cups, I expofed them on the 
outfide of a north window, where a thermometer pointed 
to 29''. The confequence was, that ice appeared firfl 
upon the boiled water ; and this, in feveral repetitions of 
the experiment, with the fame boiled water, fome of 
which 
