BANCROFT. — TERNARY MIXTURES. 365 



by Wildermanii.* That I cannot say ; but it is not true that it is a 

 necessary theoretical conclusion, and there is no proof that it is correct 

 in any case. If, instead of adding potassium bromide, we add to the 

 water some liquid in which bromine is readily soluble, the amount of 

 bromine dissolved will increase without there being any reason to 

 assume chemical action in order to account for it. Bromine is not a 

 good substance to consider, because there are so few liquids soluble in 

 water in which it dissolves without decomposition, and also because we 

 cannot ignore the solubility of the added substance in it. Let us 

 rather treat the case when we have iodine instead of bromine. Sup- 

 pose we have the system, solid iodine, a solution of iodine iu water, and 

 vapor of iodine and water; we add alcohol to tlie solution. The con- 

 centrations of the solid iodine and the iodine vapor will remain prac- 

 tically unchanged ; therefore the solubility of iodine in the water, and 

 alcohol should remain unchanged according to Wildermann. As a 

 matter of fact it does change, and I do not see how this variation can 

 be attributed to chemical action unless all solution is defined as chemi- 

 cal action, which begs the question though very possibly true. There 

 may be a radical difference between the action of the alcohol and the 

 action of potassium iodide; but that difference has not been shown. 

 As far as I can see, Wildermann's conclusions require that adding 

 alcohol to a saturated salt solution should have no effect on the concen- 

 tration of the salt because the, equilibrium between the solid salt and 

 its own vapor would remain unchanged. 



Early in this paper I proposed the word "solute" as something 

 distinct from " solvent," and it is necessary for me to justify that dis- 

 tinction. The usual way of looking at binary solutions is to consider 

 them as mixtures, and that it is purely arbitrary which of the two sub- 

 stances we consider as solvent and which as dissolved substance. The , 

 following citations will show what the prevailing opinion at the present 

 moment is. 



Lothar Meyer, after pointing out that in alcohol-water mixtures it 

 depends on the nature of the semipermeable membrane which sub- 

 stance exerts the osmotic pressure, says : t " Mit der Beschaffenheit 

 der Membran tauschen beide Stoffe die Rollen ; es ist daher eine 

 Willkiir wenn wir den einen als gelost, den anderen als das Losungs- 

 mittel bezeichnen." Ostwahl is consistent to the bitter end, saying :t 



* See Jakovkin, Zeitschr. f. ph. Cheni., XIII. 539. 1894. 

 t Zeitschr. f. ph. Chem., V. 24. 1890. 

 t Ibid., XII. 394. 1893. 



