CATALOGUE.^^HEAT, CHANGES OF FORM. 



595 



De Luc Tdees sur la met^orologie. I. ccvii. 

 II. dcvi. 



On freezing. Pure boiled water may be cooled to 14" 

 without freezing. 



Wilson's e.vperiments on cold. Ph.tr. 1781. 

 386. 



Snow was observed to evaporate at 27" F. without being 

 perceptibly cooled by it. It adhered firmly to glass at 3" ; 

 perhaps the contact of air may cause snow to melt more 

 readily, producing the increased cold which is sometimes 

 observed in it. 



♦Cavendish on Hiitchins's experiments. Ph. 

 tr. 1783. 303. 



Makes the point of congelation of mercury — asj" of 

 the Royal Society's thermometer. 



Cavendish on Macnab's experiments in 

 Hudson's bay. Ph. tr. 1786. 241. 



Finds that the sulfuric and nitric acids may be cooled mach 

 below their freezing points without congelation ; that their 

 strength rather raises than depresses their freezing points, 

 but that when diluted they seem to have two freezing 

 points, one for the acid, the other for the water, both of 

 which however depend on the strength. Thus the nitric 



acid, its strength being .56, freezes at — 30°, .53 at 



19°; .437 at — 4j°; the nitrous acid, strength .54, freezes 

 at— 3li°, .411 at— li», .38 at — 45^", ,243 at 44i», 

 .91 at— 17°: the sulfuric acid, strength .98 at— 15", 

 .629 at— 36°, .41 at— 78j°, .35 at — 68^°, .34 at — 

 6S°, .33 at— 55^°. Diluted alcohol is also similarly af- 

 fected. Mr. Macnab produced a cold of 7 g^". 



Cavendish on Macnab's further experiments. 

 Ph. tr. 1788. 166. 



Confirms his former conclusions, and those of Mr. Keir, 

 respecting the sulfuric acid ; this has a second point of 

 difficult congelation about the strength of .92, freezing at 

 about — 26°. Thus at .977 the freezing point was + 1°, 

 at .918, — 26°, at .846, + 42°, at .75S, — 45°. In Keir's 

 eiperiments the acid of the density of .848 was frozen at 

 46". 



Blagden's history of the congelation of mer- 

 cury. Ph.tr. 1783.329. 



Blagden on the cooling of water below its 

 freezing point. Ph.tr. 1788. 125. 



Boiled water is only more readily frozen when it is ren- 

 dered turbid. Sand, or broken glass, did not promote the 

 congelation, nor even agitation, unless it was minute, as 



when the inside trf the vessel was rubbed with \Tax, a little 

 water being interposed. A thin film was more easily- 

 frozen. The access of air only promotes congelation when 

 it is loaded with frozen particles ; the smallest particle of 

 ice producing the effect instantaneously. The contact o£ 

 metals seems to facilitate congelation, and the rapidity with 

 which the water Is cooled. Water expands considerably 

 when thus cooled. The greatest cold supported without 

 freezing was 20°. 



Blagden on the congelation of aqueous so- 

 lutions. Ph. tr. 1788. 277. 



The point of congelation of water with - of salt was 

 112 " 



32° ; thus, with 1 it was 4°, with ^, 2Sf. Other 



salts followed also similar laws. Crystallization did not 

 seem immediately to promote congelation. The maximum 

 of density of water with Jf of salt was about 8° above its 

 freezing point. 



Euler and Krafft on the congelation of mer- 

 cury. N. A. Pelr. 1785. III. 60. 



At about — 36" or — 40*. 

 Guthrie sur la congelation du mercure. 4. 



Petersb. 1785. 

 Keir on the congelation of the vitriolic acid. 

 Ph.tr. 1787. 267. 



Found that the sulfuric acid of the specific gravity 1.7 so, 

 fieezes at 45° F. into crystals, which are more dense than 

 1.924, perhaps more than 2, while solid, but which thaw 

 into acid of the specific gravity 1.7 80, whether the acid 

 was originallj- a little more or less dense. But when the 

 specific gravity varies as far as 1.75 or 1.81, it will not 

 freeze at 1 8° F. 



Chaptal on the congelation of sulfuric acid. 



Roz. XXXr. 468. 

 Walker. Ph. tr. 1788. 395. 



Cooled water to 10° without freezing it. 



Walker on the congelation of quicksilver in 

 England. Ph. tr. 1789. I99. 



Saussure on liquefaction. Roz. XX-XVI. 

 193. 



Williams on the expansive force of freezing- 

 water. Ed. tr. IL 23. 



Makes the expansion ^', or J^-. From the difference of 

 refractive power it might be expected to be ,', or f . 



Priestley on the air evolved in freezing. 

 Am. tr. V, 36. ' 



