152 REPORTS ON INVESTIGATIONS AND PROJECTS. 



substances can combine with water, forming a few compounds of 

 perfectly definite composition: According to the theory of hydrates 

 here advocated, a dissolved substance combines with water, forming 

 a series of hydrates having all possible amounts of water up to a 

 certain maximum quantity, the composition of the hydrates for any 

 given substance being conditioned by the concentration of the solu- 

 tion, as we would expect from the law of mass action. It has been 

 demonstrated by the boiling-point method that solvents like methyl 

 and ethyl alcohols can also combine with the dissolved substance. 



The conclusions thus far reached are based upon a study of about 

 ICO compounds, including salts, acids, bases, and neutral organic com- 

 pounds. The freezing-points, conductivities, and specific gravities 

 of about 1,500 solutions have been determined and the refractivities 

 of a large number have been measured. 



The bearing of this work on the general theory of solutions is 

 obvious. The fact that a part of the water is combined with the 

 dissolved substance and is not acting as solvent must be taken into 

 account in dealing with all solutions, and especially with concentrated 

 solutions. This accounts in large part for the abnormal behavior 

 of concentrated solutions, and is doubtless the chief reason why the 

 laws of gas pressure do not apply to the osmotic pressure of such 

 solutions. 



When the above facts are taken into account, together with such 

 factors as appear in Van der Waals's equation for gases, it will 

 probably be shown that the gas laws apply to the osmotic pressure 

 of concentrated solutions, measured under comparable conditions 

 with gas pressure, as well as to concentrated gases. 



Mofse, H. N., Johns Hopkins University, Baltimore, Maryland. 

 Grant No. 238. On the measurement of osmotic pressure. (For 

 previous reports see Year Book No. 2, p. xxx, and Year Book 

 No. 3, p. 108.) $1,500- 



Abstract of Report. — By the middle of the past year so much prog- 

 ress had been made that several cells of ideal excellence for the meas- 

 urement of osmotic pressure were ready for service, and with them 

 the determination of the pressure which is exerted by cane sugar in 

 aqueous solution was undertaken. The pressure of thirteen concen- 

 trations, varying from 0.05 to i.oo gram-molecular weight of sugar 

 dissolved in 1,000 grams of water, has been satisfactorily measured, 

 and it is believed that the results throw an entirely new light upon 



