^* arid on the Isomeric Modifications of Selenium. 501 



the whole of the naphtha was removed, and the metal having 

 been again brought to the liquid state, the thermometer was 

 plunged into it, and the heat raised to above 100 degrees. The 

 progress of the cooling of the thermometer was observed, the 

 tube being kept in the surrounding air. In a former experiment 

 the thermometer showed no rest at any point ; it descended gra- 

 dually from 100 to 20 degrees. But in constructing a delinea- 

 tion of the curve of cooling, it was easy to observe that the curve 

 completely changed its form about 55 degrees; its ordinates 

 underwent from this point a much less rapid diminution. I 

 recommenced the experiment, and agitated the thermometer 

 slightly with a view of overcoming the molecular inertia, and of 

 ascertaining the diminution of fluidity. The thermometer de- 

 scended regularly as far as the division 325 of its scale, then it rose 

 suddenly to 327*2, at which point it was steady for some seconds ; 

 it then resumed its downward march, although more slowly than 

 before. The fluidity of the metal diminished gradually ; it had a 

 buttery consistence towards 300 divisions ; but it was only at 280 

 divisions that it was no longer possible to move the thermometer. 

 The 327*2 divisions of the thermometer^ corrected for that 

 portion of the column not immersed, correspond to 55°*43. It 

 might be concluded from thence, that the temperature at which 

 the tendency to crystallization commences to increase in liquid 

 potassium is 55"*43, but that it acts with far too little energy 

 to resist the cooling, and bring about a stationary temperature, 

 as is the ease with sodium, and generally with bodies which 

 solidify suddenly. The foU owing are the series of temperatures 

 which I have observed : by taking the time as absciss, and the 

 temperature as ordinate, the curve maybe graphically represented, 

 and we can observe the influence which the heat disengaged gra- 

 dually by the solidification has had on the progress of the cooling. 



O' . . 



"" TlA '. . 



2J. . 



3 . . 



3i. . 



H . . 



5 . . 



5J . . 



6 . . 



75-42 

 71*25 

 67*48 

 63-98 

 60*61 

 57*70 

 55-24 

 55-43 

 55-10 

 54*37 

 53*74 

 52-99 

 52-25 

 51-46 



4-17 

 3-77 

 3-50 

 3-37 

 2*91 

 2*46 



0*33 

 0*73 

 0*63 

 0*75 

 0*74 

 0*79 



7 



' 2 

 8 



81 



10 



10^ 

 11 



11^ 

 12 



121 

 13 



^f^^ 50-60 



. . 49*60 



"i^i^ 48-62 



rp-4 47.53 



^^s^-) ,9V 46.45 



offtp 45-25 



milio 44-00 



'^ :^^X 42*80 

 n& ,)^i^ 4[.52 



V^-i ^40-28 

 ^'2 -:- 39*00 



.a. .., 37.72 



. . 36-50 

 . ; 35*32 



0*86 

 1*00 

 0-98 

 0*99 

 1*08 

 1*20 

 1*25 

 1*20 

 1-28 

 1*24 

 1*28 

 1*28 

 1-22 

 118 



