coding of water below its freezing Point. ] 3 1 
at which the- property commences. The experiments (hew, 
that in fome cafes the mixed water bore to be cooled as much 
below its new freezing point, as pure water below j2°; and 
with regard to the others, I think the variation was no greater 
than ufually takes place with different portions of common 
water. Scarcely any, perhaps none, of the above-mentioned 
points, were abfolutely the lowed to which the folutions or 
mixtures could have been reduced, if the experiment had been 
conducted dill more dowly and cautioufly. But however much 
they might all podibly have born to be cooled, a great dif- 
ference occurred among them in the eafe with which the ope- 
ration fucceeded. For indance, the folutions of nitre, and of 
Rochelle fait, would hardly ever fhoot till they were cooled 
many degrees below their refpe&ive freezing points, however 
negligently the operation was conduced ; whereas thofe of 
common fait, fait of tartar, and fome others, required con- 
dant attention to keep them from freezing, as foon as they 
were got four or five degrees below the point of congelation. 
Their difference in this refpedt may depend in part upon fome- 
thing unknown in the nature of each particular fait ; but 
there was one circumdance to be didin&ly traced, correfpond- 
ing to what had been obferved with pure water; namely, that 
the mod tranfparent, mod limpid folutions, were thofe which 
admitted of being cooled with the greated eafe and certainty. 
The fame obfervation holds good with regard to the mixtures : 
thus the rectified fpirit I employed adumed fomething of an 
opaline tinge upon being mixed with the water (from the fepa- 
ation of an oil it contained) and the compofition bore to be 
cooled but ill, though a film of oil, regularly fpread on its fur- 
face, would rather have retarded the freezing ; and the acid mix- 
tures, which cooled fo remarkably well, druck the eye parti- 
S 2 cularlv 
