Compounds and Densities of their Solutions. 297 



vent whose formula is given at the commencement of the line. 

 We notice that the relative solubility of a solute in several 

 solvents can change very much with the temperature. For 

 instance, acetamid is less soluble in alcohol than in water 

 between 0° and about 50°, but above 50° it is more soluble in 

 alcohol than in water. This is analogous to the relative 

 changes in vapor pressures of some liquids. We notice the 

 small increase in solubility of urethane in water as we pass 

 from 0° to 10° and the rapid increase as we pass beyond that 

 temperature. There seems to be some slight error in the 

 solubility of the aqueous solution at 30°, but there is none at 

 10°, for the solubility at that temperature was determined 

 twice. We notice also that there is no regularity in change of 

 solubility as the molecular weights of the alcoholic solvents 

 increase, whether we consider the molecular aggregations of 

 the solutesf or not. 



M. Schroederij: has deduced the equation 



in which n is the number of gram-molecules of solvent in a 

 saturated solution ; A is a constant, the same for each solute 

 whatever the solvent may be. t^ is the fusion temperature of 

 the solute and t is the temperature of saturation. How this 

 equation is obtained need not be considered. According to it, 

 the curves of solubility of any solute in all solvents should 

 coincide. Schroeder tested the equation withj?-dibrombenzene 

 in ethyl alcohol, propyl alcohol, isobutyl alcohol, ethyl ether, 

 carbon disulphid, benzene, and brom benzene ; with naphthalene 

 in benzene, chlorbenzene, and carbon-tetrachloride ; with 

 m-dinitrobenzene in benzene, brombenzene, and chloroform. 

 His results justify it, but mine do not ; only for solutions of 

 acenaphthene, naphthalene, and phenanthrene are the coinci- 

 dences at all good. 



The specific volumes of the solutions must be known before 

 we can proceed to determine the osmotic pressures of the 

 solutes, and therefore we now pass on to the densities. 



These were easily obtained by sinking a pycnometer with a 

 very small mouth into the saturated solution and drawing this 

 in, the very small mouth keeping out particles of solute. 

 Since the solution was kept stirred by air and contained an 

 abundant excess of solute and since the temperature was kept 

 constant for some ten minutes before drawing into tha pyc- 

 nometer, the solutions are to be considered in just the right 



f This Journal, 1. c. 



X Zeitschr. Phys. Chemie, xi, 449, 1893. 



