288 Dr. Blagden’s Experiments on 
faturated folution at the freezing jaoint, which therefore, when 
the congelation took place, proved to be 4% inftead of 2°, the 
number that would have anfwered to this proportion of fait. 
It has been a queftion much contefted, whether faline folutions 
depoflt their fait upon freezing. That fome feparation, or a 
tendency to feparation, takes place, many fafts concur to 
prove ; and among the reft fome phenomena obferved in the 
above-mentioned experiments. For inftance, the ftellated 
cryftals, when firft formed, were barely fufpended in the wa- 
ter, and fometimes they even gradually fubfided to the bot- 
tom ; which fhews, that they confifted of fait chiefly, only 
invifcated with ice, or at leaft of an over-proportion of fait : 
for the principal mafs of ice formed in a faturated folution 
floats in it like common ice in pure water. Befldes, it was 
almoft conftantly found, that when a cruft of ice, which had 
been formed in a faline folution, began to thaw, a thermome- 
ter thruft into it rofe fomewhat higher than the point at which 
it had become ftationary when the congelation took place ; an 
indication that a lefs proportion of fait was prefent in it than 
had been in the whole folution. And if, after any folution 
had fhot and formed a quantity of ice, the tumbler were 
ftill kept in the frigorific mixture, the thermometer immerfed 
in the liquor gradually funk lower and lower, as the congela- 
tion proceeded. But thefe very obfervations ftievv, that the 
feparation is far from perfect ; as the rife of the thermometer 
in the former cafe, or its defcent in the latter, never exceeded 
one or two degrees, under a great variation in the quantity of 
ice in the folution. 
Sometimes in folutions of fal ammoniac, and fuch other 
falts as feparate by the cooling of the water, a fort of floccu- 
leut fubftance is formed, which fubfides in the water, and 
thereby 
