SPECIFIC GRAVITY OF AQUEOUS SOLUTIONS. ARCHIBALD. 337 



calculated values based on the values of ionization-coefficients 

 for 18 C. I have, however, calculated some of the ionization- 

 coefficients, for the different salts, corresponding to 15C, by 

 using the conductivity coefficients given by Kohlrausch, and find 

 that the differences between the values for 18 and 15 are not 

 large enough to cause any appreciable error in the calculations 

 Rother seems to regard his measurements as possibly in error 

 by o to 8 in the third decimal place. He found the surface, 

 tension of the water he used to be 7.357. 



Observations of Specific Gravity. 



The specific gravity observations were all made at 18C, and 

 are referred to water at 18C. Ostwald's form of Sprengel's 

 pyknometer was used in making the measurements. It was 

 filled by dipping one arm in the solution to be measured and 

 connecting the other by means of a rubber tube with an exhaust 

 bottle. When the pyknometer had filled beyond the constant 

 volume mark on the stem, it was placed in a water bath provided 

 with a mechanical stirrer, which was connected with a w T ater 

 wheel driven by the water from a tap. The temperature of the 

 bath was not allowed to vary more than a twentieth of a degree 

 from 18. When the liquid column in the arm had remained 

 stationary for three or four minutes the meniscus was adjusted 

 to the mark, the pyknometer taken from the hath, dipped in 

 distilled water, then carefully dried with a linen cloth and 

 weighed. From several measurements of the same solution, it 

 would appear that the values of the specific gravity might be in 

 error by about 5 in the fifth decimal place. 



The lonization Coefficients. 



For simple solutions, the ionization coefficients, as in former 

 papers, were taken to be the ratios of the specific molecular 

 conductivity to the specific molecular conductivity at infinite 

 dilution. The data for finding them for the simple solutions of 

 Potassium, Sodium, and Copper Sulphates will be found in the 

 above papers. In the case of the chlorides of Potassium and 



