Speyer's—Soluhilities of Some Carbon Compoimds^ etc. 293 



Art. XXXII. — Solithilities of Some Carbon Compounds and 

 Densities of their Solutions ; by Clarence L. Speyers. 



At the present time we are more or less inclined to lind in 

 solution an action corresponding to vaporization, and as vapori- 

 zation under ideal conditions is generally considered indepen- 

 dent of the contents of the space into which the substance 

 volatilizes, chemical action of course being excluded, so in 

 forming dilute solutions we generally expect the act of solution 

 to be independent of the medium into which the solute passes, 

 that is, independent of the solvent. In some respects our 

 expectations are justified and find their expressions in the van't 

 Hoff laws; but on the other hand, we cannot fail to see that the 

 solvent plays a very important part, for many substances refuse 

 altogether to dissolve in certain solvents, and consequently the 

 simplicity of the gaseous condition cannot be carried over 

 directly to solutes without running the risk of i 

 straying away from the path leading to a satis- 

 factory explanation of solution. 



It was in the hope of finding that the different 

 molecular aggregations of the solutes would 

 explain their differences in solubility that the 

 following experiments were made. It was in 

 the hope of finding that in a saturated solution 

 the osmotic pressure of the solute in the form 

 of simple molecules would be the same in all 

 solvents because the liquid phases are all bal- 

 anced by the same solid phase, that is by the 

 same undissolved solute. The large number of 

 measurements of the solubilities of metallic 

 salts were not available on account of ionic 

 decomposition. 



The same solutes and solvents were chosen 

 which were used in determining heats of solu- 

 tion* and in determining molecular weights in 

 concentrated solutions.f 



The apparatus shown in figure 1 was used ; the tube A was 

 about IT'"' long and 2*5'^ wide; B was about 12"°^ long and 

 about 2-0^"^ wide ; C was about of the same size as B. Solu- 

 tion, excess of solute and thermometer were in A. At the 

 bottom of B was a plug of filter paper, b ; otherwise B was 

 empty, and C was empty. After the tubes were charged, they 

 were sunk in a water bath nearly to the tops of B and C. The 

 solution and solute were kept stirred by air blown through C, 

 the air escaping around the loosely fitting stopper of A. When 

 * Journ. Am. Chem. Soc, xviii, 146, 1896. f This Journal, xiii, 213, 1903. 



mr 



