Chemistry and Physics. 65 



phenomena, H representing the rise of water in the tube, h the 

 rise of the solution, M the molecular mass of the dissolved sub- 

 stance and C a constant for the particular percentage of the salt 

 used. Because salt-solutions do not follow the law of osmotic 

 pressure, nor the laws of Wtillner and Raoult, the author multi- 

 plies the formula-values by Van't Hoff's coefficient £/ and ob- 

 tains for the final values of 10,000 (H-/j)j/HM the following 

 numbers: NaCl 13-35, KC1 13*24, MgCl 2 13-26, CaCl 2 13-36, 

 SrCl 2 13-78, BaCl 2 13-77, CoCl 2 13-95, CdCl 2 13-87. The same 

 result appears when certain data obtained by Valson with a five 

 per cent solution are used to calculate the constant from the 

 above formula. This conclusion is in accord with that of Traube. 

 — Zeltschr. Physikal. Chem., v, 233, Apr., 1890. g. f. b. 



2. On a Relation between Heat of Fusion and Solubility. — In 

 consequence of the striking analogy between the osmotic pres- 

 sure of dissolved substances and ordinary gaseous pressure, an 

 analogy to which attention was first called by Van't Hoff, reason- 

 ing before applicable only to gaseous substances may now be 

 applied to solutions. Walker has sought to combine the ther- 

 modynamical equation T> T p=zp/To with the gas equation pv = 2T y 

 now applicable to solutions; and thus to deduce a relation between 

 the solubility of a substance in a given solvent and its heat of 

 fusion. The resulting differential equation dp /p = p dT /2T 2 gives 

 by integration, after multiplying by T, the expression 



Tlogp=— 1+ (log^ +-|- 



In these formulas, T is the absolute temperature, p the osmotic 

 pressure in the saturated solution, v the volume of the solution 

 and p the molecular heat of solution, assumed constant. Plotting 

 the above equation with the values of T log p as ordinates and T 

 as abscissas a straight line is obtained, the constant factor log 

 p -\-p/ 2T being the tangent of the angle which the line makes 

 with the axis of abscissas. This angle may be fixed by deter- 

 mining the solubility of the substance at two different tempera- 

 tures ; so that when one of these temperatures is the fusing point, 

 the equation is 



p=2T (tan a -logp ). 



A similar equation may be written for the fused substance, in 

 which however, the molecular heat of fusion must be added to 

 the heat of solution; so that the total heat is p+6 and the new 

 equation is 



p+o-=2T (tan a'— log p ). 

 Subtracting from this the former equation, we have 

 <7=2T (tan a'— tan a) 



by means of which a or the molecular heat of fusion may be 

 calculated. The straight line obtained by plotting the new equa- 



Am. Jour. Scr.— Third Series, Vol. XLI, No. 241.— January, 1891. 

 5 



