August 22, 1902,] 



SCIENCE. 



285 



tionary, but it represents a satisfaction of 

 the equations, which are otherwise inde- 

 terminate. The preliminary paper contains 

 sixty-sis verifications of the new law'. 



On Conductivity: Geo. A. Hulett. 



1. Advantages of saturated solutions as 

 a basis for conductivity of electrolytes. 



2. The values for saturated solutions of 

 gypsum are of the correct magnitude for 

 determining the capacity of conductivity 

 cells, and have been proposed by Kohl- 

 rausch, but his results are affected by sur- 

 face tension. 



3. Definiteness and reproducibility of 

 normally saturated solutions, and the equa- 

 tion 



(Xt = .002206 -I- .0000456 ( « — 25) 



4- .000000163 (« — 25)^) 



for normally saturated solutions from 10° 

 to 30° calculated from observed data. 



4. Sources of error in the Arrhenius cells 

 and water conductivity. 



Beziehung zwischen osmotischem Druckund 

 negativem Druck {Relation hetiveen Os- 

 motic Pressure and Negative Pressure) : 

 George A. Hulett. 



1. It will be necessary here to go some- 

 what into detail concerning the important 

 property of liquids known as negative 

 pressure (or better perhaps, tensile strength 

 of liquids) reviewing the work of Berthelot 

 (All. chim. phys. (3), 30, 232), Worthing- 

 ton {Phil. Trans., 1893), Jolly and Nixon. 



2. The dissolved substance, under the in- 

 fluence of osmotic pressure, diffuses to the 

 boundary of the solvent, where it first finds 

 'foothold' and exerts a pressure normally 

 to the surface equal to the osmotic pres- 

 sure, and this is a negative pressure on the 

 solvent since it tends to increase the volume 

 of the solvent. This pressure is resisted by 

 the tensile strength of the solvent (which 

 has been measured directly by Worthington 

 and Hulett). 



3. A solution in equilibrium with its 

 vapor must then be considered as a system 

 with unequal pressures on the two phases. 

 The vapor is subjected only to its own 

 equilibrium pressure, while the liquid is 

 subjected to a very considerable negative 

 pressure (equal to the osmotic pressure). 



Such a system, considered from the stand- 

 point of thermodynamics, shows a relation 

 between the negative pressure, molecular 

 volume of the solvent and volume occupied 



by a gram molecule of the vapor, I ^ = — I . 



This shows ivhy osmotic pressure lowers the 

 vapor pressure, while the van't Hoff equa- 



tion /f = — — shows only that J is propor- 

 tional to BT- and l/l , and it seems that 

 this is only indirectly proportional. 



4. Calculation by means of the equation 

 from known data, of the change of vapor 

 pressure due to a given osmotic pressure 

 and comparison with the known changes. 



5. The experimental work consists in the 

 direct observation of change of vapor pres- 

 sure when negative pressure is applied 

 mechanically to the liquid alone, with a 

 brief description of the apparatus. 



The Expansion of a Gas into a Vacuum and 

 the Kinetic Theory of Gases: Petee 

 Fireman. 



The expansion of a gas into a vacuum 

 is accompanied by no change of energy. If, 

 however, the experiment is carried out by 

 means of two communicating vessels of 

 equal size, one containing a gas under a 

 given pressure and the other being vacuous, 

 then, on allowing the gas to enter into the 

 vacuous vessel, we observe a rise of tem- 

 perature in the latter and an equal fall of 

 temperature in the foi'mer. Why so? A 

 plausible explanation would be perhaps 

 this : As soon as a little of the gas has 

 entered the empty vessel the rest of the gas 

 will do work on it, causing a rise of the tern- 



