J2 Conductivity of Aqueous Solutions. Part II. 



arises from this source was shown by direct experiments. For example, 

 when two or more specific-volume determinations were made, the amount 

 of solution taken in the different experiments was purposely varied, so that 

 the vapor space should vary from about 1.8 c.cm. to 1 c.cm. If, now, a 

 considerable amount of the water were present in the vapor space, the 

 specific-volume values obtained would, of course, be larger the smaller that 

 space. As a matter of fact, however, the values obtained with the 1 c.cm. 

 vapor space were as often smaller as they were larger than those obtained 

 with the 1.8 c.cm. vapor space. In other words, no difference greater than 

 the variable experimental error was observed. The error due to this source 

 is therefore probably less than 0.1 per cent. 



(7) The temperature measurements may be regarded as accurate to 

 within 0.2 ; and this of itself introduces an uncertainty of only 0.07 per 

 cent in the worst case, that of the 306 values. That the bomb and its con- 

 tents actually attained the temperature of the surrounding vapor is shown 

 by the fact that the extremely sensitive reading of the upper electrode 

 remained constant indefinitely after it had once become so ; and by the fact 

 that there could not be a continuous loss of heat of appreciable magnitude 

 from the bomb to the surroundings, since upon the sides the bomb was 

 protected against radiation and cold convection-currents by the iron shield 

 with the vapor outside, and since above there was always a layer of vapor 

 10 cm. in height, and since the dropping back of condensed liquid onto the 

 bomb was prevented by the mica shield ; moreover, the copper lead-wires 

 were only 1.2 mm. in diameter and passed through the upper layer of 

 vapor before emerging. 



(8) Another possible source of error might be the gathering of vapor 

 bubbles on the under surface of the cover, whereby the apparent volume 

 of the liquid would be increased. That this did not occur was shown by 

 removing the bomb from the heater, shaking vigorously, immediately 

 replacing it, and taking conductivity readings as soon as the temperature 

 had again become constant, whereby the same readings were obtained as 

 before the shaking. 



(9) The air was not entirely removed from the bomb at the start, and, 

 as the solution expands, and the temperature rises, the air pressure 

 increases. Assuming that the preliminary boiling had removed all of the 

 air from the solution in the beginning, and that there is no solubility of the 

 air in the liquid at the high temperatures, its pressure can be calculated 

 by the gas laws. At the temperatures of 218, 281, and 306, it would 

 thus amount to about 1, 2, and 2.5 atmospheres respectively. The effect 

 of these air pressures on the specific-volume values can not be calculated, 

 since the compressibility at these temperatures is not known ; but for 

 these small pressures it is undoubtedly less than the errors of observation. 



