270 PETTEJiSSON, ON WATER AND ICE. 



inelting point, ci the specific heat of the solid, c of tbe liqnid 

 body, tlien tlie variation in the kitent lieat may be expressed by 



dr 

 (It 



Cl — c 



According to Person the specific heat of ice is half of that 

 of the water, then 



,lt~— ^^-^ 

 i.e. the latent heat of water will bo found O.5 calory smaller 

 for every centigrade degree below zero. 



By the calorimetric method just described these varia- 

 tions, predicted by theory, can be experimentally verified. The 

 experiments relating to pure water are published in the Ofvers. 

 K. V. A. Förhandl. 1878. It now remains to be seen, if salt 

 ivater by freezing shows any remarkable anomaly with regard 

 to its latent heat. Chapter G will be reserved for this subject. 



D. Determinations of freezing points and specific 

 gravity etc. 



The freezing point of each water was first roughly ascer- 

 tained by a preliminary experiment with an ordinary thermom- 

 eter. Afterwards a considerable quantity was slowly cooled 

 to about 0°.2 or 0°.3 C below its normal freezing point, then a 

 crystal of snow was thrown into the beaker and the maximum 

 of temperature observed by means of a Geissler thermometer. 

 During the whole process the water was constantly mixed. 



The following table shows the relation between the specific 

 weights and the freezing points of different kinds of sea-water 



(T = spec. gravity at— -73 Ja r = freezing point Jr ^ 



1.0271 I 1°.895 I 



> 0.0027 O'. 18 0.0150- 



1.0244 

 1.0148 

 1.0122 

 1.0104 



0°.175 —0.0148 



I 0.009G j 0*.69 — 0.013!> 



-r.025 



0.002G [ . , 



^ — 0.°85 ^ 



j 0.0018 \ 0°.135 —0.013 



\ 0.00G3 I . 



1.0041 J — 0°.27 J 



0°.445 — 0. 



0141- 



medium = — 0.oi4a 



