August 23, 1907] 



SCIENCE 



241 



The Ignition Temperatures of Gaseous 

 Mixtures: K. George Falk, Columbia 

 University. 



The method of determining the ignition 

 temperatures of gaseous mixtures by cal- 

 culating the rise in temperature, produced 

 by the adiabatic compression of the gases, 

 by means of the formula 



in which Fj and V2 denote the initial and 

 final volumes of the mixture, Tj the initial 

 temperature, T2 the ignition temperature, 

 and k the ratio of the specific heats of the 

 gases at constant pressure and constant 

 volume, was applied to mixtures of carbon 

 monoxide and oxygen and the following 

 results obtained : 



r, (absolute) 



1 CO + O: 911 



2 CO + O2 879 



4 CO + O, 907 



6 CO + 0, 1002 



The Theory of "direct" Determinations of 



Migration: W. Lash Millek, University 



of Toronto. 



The relations between concentrations of 

 solutions, transport numbers, and motion 

 of the boundary, may be deduced without 

 introducing time or functions dependent on 

 it (conductivity, mobility). 



This method of treatment makes the rela- 

 tions between the direct and the analytical 

 methods very clear, and shows how the di- 

 rect method may be applied to solutions of 

 weak acids, etc., without reference to their 

 degree of dissociation. 



A Comparison of Collodion, Parchment 

 Paper and Gold-ieater's Skin Mem- 

 branes with Porcelain: S. Lawrence 

 BiGELOW, University of Michigan. 

 Methods for making collodion membranes 



were investigated and developed. 



Some colloids were separated from crys- 



talloids, using the three above-mentioned 

 membranes. The progress of dialysis was 

 followed by the conductivity method, and 

 it was found to occur fastest with gold- 

 beater's skin, slower with collodion and 

 slowest with parchment paper. The results 

 indicate that collodion is to be preferred to 

 parchment for dialyzing. 



The rates at which water permeated the 

 above-mentioned substances under different 

 pressures and temperatures were deter- 

 mined. The "permeabilities" were ex- 

 pressed in cubic millimeters of water pass- 

 ing through one square centimeter of mem- 

 brane per minute. When these values for 

 permeability were laid off as ordinates, 

 against corresponding pressures and tem- 

 peratures, respectively, as abscissa, straight 

 lines were obtained for pressures, nearly 

 straight lines for temperatures. This is 

 what would be expected if Poisseuille's 

 formula for the passage of liquids through 

 capillaries applied. More significant than 

 the application of the formula is the fact 

 that the "picture" for porcelain under the 

 same conditions so strongly resembles those 

 for the three membranes. This is evidence, 

 though not by any means conclusive, in 

 favor of the view that the passage of water 

 through membranes is a capillary process. 



The article will appear shortly in one of 

 the journals. 



The Equilibrium Diagram for the Series 

 Copper-Aluminum: B. E. Curry, Cor- 

 nell University. 



The freezing point curve for this series 

 consists of seven branches. Six series of 

 solid solutions and one compound, CuAL, 

 separate from the melt. The y8 and S 

 series of solid solutions are instable at the 

 lower temperatures. 



Electrolytic Separation of Silver from 

 Copper: H. W. GujLett, Cornell Uni- 

 versity. 



