130 Dr. Blagden’s Experiments on the 
earthy bafis, a iolution of the common bitter purging fait, 
whofe freezing point was at 25°!, bore to be cooled to 19 0 . 
Acids, iis I have already had occafion to remark, rather 
augment this quality of being cooled below the freezing point. 
A combination of nitrous acid with diftilled water, in fucli 
proportions that the new freezing point was between i8°and 
1 9 0 , funk down to 6° before it congealed; which being fully 
1 2 degrees of cooling, is greater than I have been able to 
produce with pure water. Another mixture of the fame kind,* 
fo ftrong as to have its freezing point about 1 1°, cooled down 
to i°. A mixture of vitriolic acid and diftilled water, whofe 
freezing point was 24 0 !, cooled to 14®; and one with the acid 
of fait, having its freezing point at 25% funk to 16° before 
it froze. It is here to be obferved, that thefe acid mixtures 
were rather remarkable for the fteadinefs with which they 
bore to be cooled, and the little tendency they fhewed to fhoot 
before they were funk much below the freezing point, than 
for exceeding the number of degrees which pure water might 
be cooled. Of the alkalies, a folution of tartar, whofe freez- 
ing point was 2 5°!, cooled to 18°; and another, with the 
freezing point at 1 5 0 , funk to 8°. A folution of cryflallifed 
foda, freezing point 30°, cooled to 21 0 ; and a folution of 
mild volatile alkali, freezing point 19°, to n°. A mixture 
of rectified fpirit of wine and water, whofe freezing point 
was 12°, cooled to 5 0 ; and another, with the freezing point 
at 8°!, to 2*. 
All thefe fads, with many others of the fame nature which 
I obferved, fufficiently (hew, that foreign fubftances, chemi- 
cally combined with or diffolved in water, do not take away 
its property of being cooled below its point of congelation ; 
though, by depreffing that point, they alter the degree of cold 
at 
