THE CHEMICAL PROBLEMS OF TO-DAY. 371 



dilute solutions behave iu regard to the molecular state of the dissolved 

 siibstauce like gases. 



Ill this manner new methods are given for the determination of molec- 

 ular weights, which we are now able to determine by means of meas- 

 urements relating to tho, freezing pointy the vapor pressure^ or the osmotic 

 pressure of a solution of the substance to be tested. 



These results are of the highest possible practical importance for chem- 

 istry, since they widen in an unexpected manner the possibility of the 

 determination of molecular weights, and in a still higher degree we are 

 surprised by the elucidation which they offer in regard to the nature of 

 solution. Clausius had already admitted, within narrower limits, that 

 in solutions of electrolytes some of the dissolved molecules were decom- 

 posed into their ions, but now this has been proved in a larger measure, 

 particularly by Arrhenius. What a change our conceptions will have 

 to undergo if we have to accustom ourselves to regard a dilute solution 

 of sodium chloride as one containing, not uudecomposed molecules of 

 this salt, but separated atoms of sodium and chlorine! 



We owe these revolutionizing innovations to the investigations of 

 vau't Hoff", Arrhenius, Ostwald, Planck and de Vrie, but iu regard to 

 experimental research especially to the splendid work of Raoult, which 

 during recent years has etfected this mighty theoretical progress. 



Thus we see physical chemistry moving on in weighty development. 

 Special laboratories are opened for her, and a special journal also has 

 been started which is open alike to the records of experiment and to 

 theoretical discussion. Through the foundation of this organ physical 

 chemistry has been furthered in a most active manner. All the 

 questions of the time and all those in dispute belonging to this depart- 

 ment of science receive in this paper a thorough discussion. Dynamical- 

 chemical questions are successfully studied, a significant impetus is 

 given to the study of structure and affinity (widened as our knowledge 

 of the nature of solutions has made necessary), by means of the study 

 of the relations between chemical nature and electric conduction. 



The inquiry into the intimate relations that exist between physical 

 and chemical prui)erties, which was inaugurated half a century ago by 

 Hermann Kopp, is now being deepened and widened. 



It is true that the great hopes which sprang from the study of thermo- 

 chemical questions have so far been only partly fulfilled, but consecutive 

 measurements offer more clearness also iu this case. 



There is no field of our scnence in which we may expect greater revo- 

 lutions in the time near at hand than in that of j)hysical chemistry! 

 The value of these for general chemistry will be greater in proi>ortion 

 as the representatives of the same will recognize their task in tliis: 

 Above all to remain upon the chemical standpoint and to improve chem- 

 istry by the ajiplication of physical modes of thought and experiment. 

 Those who tried to further the progress of chemistry by the use of 

 physical methods, but with insufficient consideration for chemical rela- 



