-438 LAWSON CHEMICAL RELATIONS OF HEAT. 



^ mixture of old frozen snow and salt (newly-fallen snow does not 

 answer well,) the sulphur dioxide gas is easily condensed to a 

 liquid, which is heavier than water, sp. gr.==2-38). The boiling 

 temperature of this liquid, however, is 14°, and when in sealed 

 tubes (if the temperature be raised to 60°, that of ordinary air) it 

 exerts a pressure of 2J atmospheres. At between 105° and 110° 

 below zero the liquid freezes into solid crystals, which are heavier 

 than the liquid. To succeed perfectly in showing the boiling of 

 the liquid dioxide by heat of the hand, it is necessary to have a 

 twist of cotton, enveloping freezing mixture, around the top of the 

 tube, to provide for rapid condensation ; or the tube may be fitted 

 with an encircling short piece of much wider tube at the top to 

 contain the freezing mixture. 



The next experiment was a very remarkable one. A platinum 

 crucible was made red-hot, the dioxide was thrown into it, and 

 immediately passed into the spheroidal state, water was added, and 

 the red-hot crucible became filled with ice — the whole having cool- 

 ed down in half a minute from red-hot to a temperature far below 

 freezino^, and under favorable circumstances it would reach 40° 

 below zero, so that even mercury could be frozen. 



Professor Lawson, in referring to the great opportunities which 

 we have in this climate of studying the eflfects of heat, exhibited a 

 large bottle containing several pounds of glacial sulphuric acid, that 

 had separated and crystallized spontaneously from a solution of 

 ferrous sulphate in oil of vitriol during the recent severe weather. 

 The small portion of solution left in the bottle had a sp. gr. of 1.612. 



