Experiments on freezing Mixtures. 247 
It is well known, that fpirit of wine expands more by g. 
given number of degrees of a mercurial thermometer in warm 
temperatures than in cold ones ; and this inequality, as might 
be expected, was lefs in the ftronger fpirit than in the weaker, 
but the difference was inconfiderable, The oil of faffafras alfo 
had fome of this inequality, but much lefs. It however ap- 
pears to be by no means a proper fluid for filling thermometers 
with. No appearance was obferved which indicates any confi- 
derable irregularity in the contraction of fpirits of wine in in- 
tenfe cold, or which renders it probable, that thermometers 
filled therewith could be funk by a mixture of fnow and fpirit 
of nitre to a degree near approaching to that mentioned by 
Profeflor Braun. 
6. Mr. M c Nab in his experiments fometimes ufed one 
thermometer and fometimes another; but in the following 
pages I have reduced all the obfervations to the fame ftandard ; 
namely, in degrees of cold lefs than that of freezing mercury 
I have fet down that degree which would have been (hewn by 
the mercurial thermometer in the fame circumftances ; but as 
that could not have been done in greater degrees of cold, as the 
mercurial thermometer then becomes of no ufe, I found how 
much lower the mercurial thermometer flood at its freezing 
point, than each of the fpirit thermometers, and increafed the 
cold (hewn by the latter by that difference. 
On the common and dephlogijlicated Acids of Nitre . 
The following experiments (hew, that both thefe acids are 
capable of a kind of congelation, in which the whole, and not 
merely the watery part, freezes. Their freezing point alfo 
differs 
