KAHLENBERG — ACTION OF SOLUTIONS ON TASTE. 5 



•well as from the osmotic pressure, the freezing point, or the 

 boiling point of its solution, the results are generally identical. 

 Instances where double or even more complex molecules are 

 formed when substances are dissolved in water are known, and 

 yet these are perhaps not much more common than cases of 

 polymerization in the gaseous state. The analogy that exists be- 

 tween gases and solutions of non-electrolytes is almost perfect. 

 This appears clearly when we regard the statement of Avogadro 

 — equal volumes of all gases under the same conditions of tem- 

 perature and pressure contain an equal number of molecules — 

 in conjunction with this statement modified through the work 

 of van't HofT so as to apply to solutions, — equal volumes of so- 

 lutions having the same temperature and the same osmotic pres- 

 sure contain an equal number of molecules, which number is 

 identical with that contained in a gas having tha same volume 

 and temperature as the solution and a pressure equal to the os- 

 motic pressure of the latter. 



The solutions that conduct electricity on the other hand are 

 different in character. From what has been said, it is clear that 

 these solutions are such as contain the ordinary salts, acids, and 

 bases. These substances do not exist in aqueous solutions in the 

 molecular condition represented by their chemical formulas as 

 ordinarily written. The osmotic pressure, the lowering of the 

 freezing-point, and the elevation of the boiling-point of these 

 solutions are all greater than they would be if the substances 

 when in solution possessed the molecular weight indicated by the 

 usual formulae. According to the theory of Arrhenius these 

 substances exist in solution in a partially dissociated state; this 

 explains the peculiar behavior of these solutions as compared 

 with those of non-electrolytes. The degree or extent of this 

 dissociation depends on the nature of the dissolved substance and 

 the concentration of the solution. Theoretically the dissocia- 

 tion is complete only at infinite dilution; many substances, how- 

 ever, are so strongly dissociated when dissolved in water that 

 dissociation is practically complete at finite dilutions. The part- 

 molecules into which the dissolved molecules are dissociated are 



