248 Mr. Cavendish’s Account of fome 
differs greatly according to the ftrength, and varies according 
to a very unexpected law* Like water too they bear being 
cooled very much below their freezing point before the conge- 
lation begins, and as foon as that takes place, immediately rife 
up to the freezing point. 
7. On the morning of Feb. 1. the common and dephlo- 
gifticated fpirits of nitre, N® 142 and 141, whofe fpecific gra- 
vities were 1,4043 and 1,4033, were found clear and fluid, 
the cold of the air at that time being - 47 0 . They alfo bore 
being fhook without any alteration ; but on taking out their 
froppers, both of tlrem in a few minutes began to freeze, the 
congelation beginning by a white appearance at top, which 
gradually fpread to the bottom ; and they became fo thick as 
not to move on inclining the phial. For want of a thermo- 
meter whofe ball reached far enough below its fcale, Mr. 
M c Nab was not able to determine their cold while in the 
bottle ; but in fomewhat more than an hour’s time, the frozen 
acid had fo much fubfided as to admit of his pouring a little 
fluid matter out of each into a glafs with a thermometer in .. 
it*; whereby the cold of the common fpirit of nitre was 
found to be - 3 i°f , and that of the dephlogifticated acid — 30°, 
the temperature of the air being — 4 1°. Each of thefe de- 
canted liquors, at the time their .temperature was tried, was 
full of fmall fpicula of ice : they were then put into phials 
well flopped, and they, as well as the undecanted liquors, fent 
home to be examined. The decanted part of the common 
* It may be a Iked, why* it was more poffible to decant any liquor at this time 
than at firft, as the acid was all the w'hde expofed to a cold much below the 
freezing point ? The reafon in all probability is, not that any part of the ice firfl 
'’or tried diffolved, but that the fmall filaments into which it fhot colledted toge- 
ther, and in fome. meafure fubfided to the bottom. 
fpirit 
1 
