coding of JFater below its freezing Point. 129 
I he efte£t of this want of transparency was very different 
from that of chemical mixture, as appeared by fubfequent 
experiments. 
Though the property of being cooled below the freezing point 
appeared to belong eflentially to water in its pure ftate, it was pro- 
bable that it would be in fome meafure altered or modified by 
the various fubftances which are capable or being diflolved in, 
^or chemically combining with, the water. But here a further 
circumflance came to be confidered. It is well known, that 
fuch fubftances, uniting with water, have a power of lower* 
ing its point of congelation a greater or lefs number of de- 
grees, according to the nature and quantity of the fubftance 
employed. The firft object, therefore, was to determine in what 
manner the property of bearing to be cooled would be affected 
with regard to that new point of congelation. For this pur- 
pofe I made many experiments with feveral different fubftances, 
which it would be too long to relate in detail, but the princi- 
pal were as follows. 
Having diflolved in diftilled water as much common fait as 
lowered its freezing point to 28% I cooled it to 1 8°-f before it 
congealed. Another folution of the fame fait, whofe freezing 
point was 16°, bore to be cooled to 9 0 ; and a ftronger folution, 
whofe freezing point was 13°!, cooled to 5 0 before it fhot. A 
folution of nitre, whofe freezing point was 27 0 , cooled to 16°, 
that is, eleven degrees below its new freezing point; a folu- 
tion of fal ammoniac, whofe freezing point was 1 2% cooled 
to 3 0 ; and one of Rochelle fait, freezing point 27T, buffered 
the thermometer to fink in it to 1 6° before it froze ; a cooling- 
equal to the greateft I ever obtained with the pureft diftilled 
water boiled. A folution of green vitriol, whofe freezing 
point was near 30°, cooled below ip°: and, of fal ts with an 
Vol. LXXVIII. S earthy 
