518 BEPOKT— 1888. 



is below 0°. No liquid besides water showed in Amagat's experiments 

 any sign of a point of maximum density ; the peculiarities associated with 

 this point in the case of water seem to cease at pressures above 3,000 

 atmos., and water at higher pressures behaves like other liquids ; the 

 liquids examined were ether ; methyl, ethyl, propyl, and allyl alcohols, 

 ethyl chloride, bromide, and iodide, carbon bisulphide, and phosphorous 

 chloride. 



Solidification of Liquids ly Fressure. 



Of the many liquids subjected to great pressure, Amagat ^ had not 

 succeeded in solidifying one; at last the compound 0.2014 was found to 

 solidify at a great pressure, the temperature of solidification rising with 

 increase of pressure ; the temperature of solidification is the freezing- 

 point of the liquid and the melting-point of the solid ; in the exceptional 

 case of water, which expands on freezing, the melting-point of ice was 

 expected by theory and found by experiment to be lowered by px'essnre ; 

 in the case O2OI4, the temjDerature of solidification, which at atmospheric 

 pressure is much below 0°, rises with increased pressure as Amagat 

 found, the solid having a very distinct crystalline structure. The fol- 

 lowing are among Amagat's results for pressures and freezing-points of 

 this body : — 



Pressure in atmos. . . 210; 620; 900; 1,160 



temperature . . . -19°-5; 0°; 10° ; 19° 5 



Benzene solidified at 22° under about 700 atmos. Amagat considers it 

 not improbable that every liquid has a ' critical ' temperature of solidifica- 

 tion — i.e., one above which no pressure, however great, will convert the 

 liquid into a solid. 



Compressihility of Solids and Liquids. 



The general discussion of this problem up to his time, and experiments 

 by himself on the compressibility of water, mercury, and of glass, brass, 

 and copper, are given by Regnault.- In Tait's ' Properties of Matter ' 

 (1685) there is an historical account, including and supplementing that 

 by Regnault, a critical discussion of theory and experiment on the 

 subject, and of advances in it made since Regnault's time. 



The reader interested in this part of the subject cannot do better than 

 consult this excellent summary by Professor Tait. 



References are here given to papers by Oersted, Perkins, Colladon, 

 and Sturm, Poisson, Aime, before Regnault's researches ; also to Wertheim, 

 Grassi ; to a paper by Oailletet, and one by Pagliani and Viccntini. 



To these must be added papers by Voigt, Rontgen and Schneider, 

 Braun, and Tait.^ 



1 a E. 105, 1887, p. 163; Phil. Mag. 2i, 1887, p. 44G; C. S. J. Abs. 1887, 

 p. 1013. 



= Mem. de VAcad. 21, p. 429. 



= Oersted, Ann. CMm. 2, 21, 1822, p. 99 ; 22, 1S23, p. 192 ; 28, 1828, p. 326 ; Mem. 

 Boy. Soc. Copenhagen. Perkins, Phil. Trans. 1820; Ann. CMm,. 2, 1(5,1821, p. 321; 

 23, 1823, p. 410. Colladon and Sturm, Ann. Ch.im. 2, 3G, 1827, pp. 113, 225 ; jMem. 

 des Etrangers, 1, 5. Aime, An7i. Chlm. 3, 8, 1843, p. 257. Wertheim, Aim. CMm. 

 .3, 23, 1848, p. 52. Grassi, tIww. CAm. 3, 31, 1851, p. 437. Cailletet, <7. i?. 75, 1872. 

 p. 77. Pagliani and Vicentini, Sulla CompresnWita dei LiqvidifTovim, 1884. Voigt 

 Wied. An)i. JErgid.l,-^. 214. Kontgen and Schneider, IRet?. J.?m. 1886-1888, 29, 



