VOL. LXXVI.] PHILOSOPHICAL TRANSACTIONS. ' 107 



the ball being soldered fast to the tube of the thermometer 7-r lines above its 

 reason of the greater degree of cold produced in this than in the preceding ex- 

 periment is, that the acid was in a state of congelation : for as the congealed 

 acid united to the snow and became fluid by the union, it is plain, that cold must 

 have been produced both by the melting of the snow and by that of the acid. 

 The day before, Mr. M'Nab, by adding snow to some of the same acid in the 

 usual manner, when the cold of the materials was — 4&^j produced a cold of 

 only - 66°. 



In these last 4 experiments the acid was reduced, by the addition of the snow, 

 to the strengths of .325, .343, .403, and .334 ; and the cold produced in them 

 was before said to be — 55^4-, — 08%, — 78°4-, and — 66°; whence we may 

 conclude, that these are nearly the points of aqueous congelation answering to 

 the foregoing strengths ; only it appears that the strengths here set down are all 

 of them rather too small. 



On the mixture of oil of vitriol and spirit of nitre. — ^This mixture is not so fit 

 for producing cold by the addition of snow, as oil of vitriol alone ; for the cold 

 obtained did not exceed — 54%, in either of the experiments tried with it. The 

 point of spirituous congelation of this mixture, when diluted with somewhat 

 more than -^V of its weight of water, is about — 20°, and is much lower when 

 the acid is considerably more diluted. 



On the Spirit of Wine. — The rectified spirits N'' 8 were diluted with snow, in 

 the same manner as the other liquors ; but were found not to want any, as the 

 first and only addition of snow produced cold. The quantity added was about 

 ■^-^ of the weight of the spirit. The spirit thus diluted was divided, like ^he 

 other liquors, into 2 parts, and each tried separately. The first was at — 45^ ^ 

 before the addition of the snow, and was sunk by the process to — 56^, The 

 snow, even at the first addition, did not dissolve well, so that the spirit imme- 

 diately became full of white spots, and grew thick by the time it arrived at its 

 greatest degree of cold. After standing some hours^ the mixture rose to the 

 temperature of — 39°, and was got clear, but yet was not limpid, but of the 

 consistence of syrup. No cold was produced by adding snow to it in that state, 

 though it appeared that its point of aqueous congelation was at least 6° lower 

 than its temperature at that time : which seems to show that spirit of wine has 

 scarce any power of dissolving snow when it wants even 6° of its point of aque- 

 ous congelation, and therefore is another instance that snow is dissolved much 

 less readily by spirit of wine than by the nitrous and vitriolic acids. In trying 

 the other part of the diluted spirits, the cold produced was only — 4']°\, the 

 cold set out with being — 37°. 



It appeared by the diluted spirit of wine N° 143, which on Dec. 12 froze by 

 the natural cold of the atmosphere, and was treated in the same manner as the 



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