1817.] Dilatation of Liquids at all Temperatures. 369 
Mercurial Salt water thermometer. 
Liquid. therm, 
cy Calculated, | Observed. | Difference: 
sO $0:00 80:0 0:00 
70 65°29 68'4. +0°11 
60 57°10 57°1 0:00 
Bibra a{ 80 46-42 | 466 | +018 
with 40 36°22 36°3 +0°08 
a 30 26°50 26°5 0:00 
sale 20 Wire 17°3 + 0°07 
F 10 $4] 84 —O-°0L 
10) 0:00 0:0 0:00 
—10 —800 |. —80 0:00 
The agreement of observation with the formula is as exact as 
could be desired. In this case the contraction was observed below 
zero by means of freezing mixtures, and we see that calculation 
agrees with experiment at that point likewise. This solution con- 
geals, also, without dilating; for the equation of the maximum is 
0 = 0°820006 + 0:004055 T + 0°000008325 T? 
the two roots of which are imaginary. Hence water saturated with 
common salt loses the property of dilating before it becomes solid. 
It would be interesting to verify this result by experiment ;* for, 
though it is founded on a strong analogy, since the law of dilatation 
holds at — 10° Reaumur, yet it can be considered ouly in the light 
of a very probable hypothesis. But to make the experiment exactly, 
the thermometer should be completely freed from air, and it should 
he cooled slowly, that the liquid may remain fluid even when below 
the freezing point. 
Sir Charles Blagden made an observation of this kind, of which 
an account is given in his interesting memoir on the degree of the 
congelation of water; but the solution which he employed was not 
saturated. It contained 4°8 parts of water for one of salt. Con- 
sequently its congelation took place at — 10°37°, according to the 
law which Blagden discovered. This solution contracted in cooling 
to — 667°; but when cooled down to — 7°55°, it appeared to 
dilate sensibly. These limits are considerably above — 10°, at 
which Deluc tried the saturated solution which formed his thermo- 
meter. Hence the experiment of Blagden cannot in the least in- 
jure the law which we have found for the solution which Deluc 
employed. It is very likely that a certain proportion of salt deprives 
water of the property of dilating before congelation, and that a 
* Such an experiment could hardly be made, as water parts with its salt in the 
act of congealing.—T. 
Vor. 1X. N° V, 2A 
