July 7, 1911] 



SCIENCE 



31 



(Abstracts furnished by the authors.) 



Eighty-eight new names were added to the roll 

 of membership. The meeting of 1912 will be held 

 at the State Historical Building in Des Moines, 

 and will be a meeting celebrating the twenty-fifth 

 anniversary of the organization of the academy. 



Officers elected for the ensuing year are: 



President — Louis Begeman, Cedar Falls. 



First Vice-president — A. A. Bennett, Ames. 



Second Vice-president- — C. N. Kinney, Des 

 Moines. 



Secretary — L. 8. Eoss, Des Moines. 



Treasurer — G. F. Kay, Iowa City. 



Members of the Executive Committee — H. S. 

 Conard, Crinnell; B. H. Bailey, Cedar Rapids; 

 H. M. Kelley, Mt. Vernon. 



L. S. Boss, 

 Secretary 



SOCIETIES AND ACADEMIES 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON 



The 696th meeting was held on May 20, 1911, 

 Vice-president Fischer in the chair. Three papers 

 were read. 



Experiments with Different Types of Voltameters: 

 Mr. G. W. ViNAL, of the Bureau of Standards. 

 According to Faraday 's law for electrolytes the 

 deposits of silver in different types of voltameters 

 should be equal when the same number of cou- 

 lombs of electricity has passed through each, pro- 

 vided, however, that there are no secondary reac- 

 tions taking place. Differences in weight and 

 appearance have been observed, particularly be- 

 tween the porous cup and filter paper forms. "We 

 have endeavored to find an explanation of these 

 effects and to push the accuracy of our measure- 

 ments beyond the limits hitherto attained. A con- 

 stant temperature balance room has obviated the 

 difficulties usually encountered in weighing the 

 platinum bowls. The current has been measured 

 by balancing the po'^ential drop across a standard 

 resistance against the voltage of a Weston cell 

 and also by the potentiometer method. The purity 

 of the electrolyte is of great importance and the 

 tests will be discussed elsewhere. 



The Kohlrausch, or no septum form as we have 

 used it, consists of a glass dish under the anode 

 and a ring of glass in the surface of the liquid 

 to prevent the slime formed during electrolysis 

 from reaching the cathode. 



The siphon voltameter is unsatisfactory even 

 when short siphons of large diameters are used, 

 owing to the heating and large volume of electro- 



lyte which may yield erroneous results if the 

 electrolyte is not quite pure. 



The filter paper form devised by Lord Rayleigh 

 employs a sheet of filter paper to separate the 

 anode and cathode. We have found the deposits 

 in it abnormally heavy and striated in appearance, 

 which effects are due to the filter paper not being 

 chemically inert. Striated deposits are always 

 heavy. We have studied the cause for striations 

 and find two conditions to be necessary and suffi- 

 cient for their production, viz., (1) the presence 

 of reducing impurities in the electrolyte, (2) the 

 motion of the liquid over the face of the cathode. 

 When both of these conditions are fulfilled we 

 may suppose any given initial distribution of 

 points of silver which will grow in the direction 

 of the liquid currents (usually vertical) since the 

 crystalline structure is destroyed by colloidal de- 

 posits. In this way a crystal grows into the one 

 above it and eventually a striation is formed. 

 The initial spacing of the crystals and conse- 

 quently the spacing of the striations is dependent 

 on the current density. 



T. W. Richards has advocated the use of a 

 porous cup instead of filter paper to more per- 

 fectly separate the anode and cathode liquids. He 

 gave as a reason for this substitution that a heavy 

 complex ion could pass through the filter paper 

 and increase the weight of deposit, but we have 

 found that by using two or three thicknesses of 

 filter paper the effect instead of being diminished 

 is materially increased. The evidence of our work 

 does not support the complex ion theory. 



We have used two sizes of porous cup voltam- 

 eters and find that with electrolytes, a trifle im- 

 pure, that the larger will give the heavier deposit. 

 This phenomenon we have called the ' ' volume 

 effect. " It is a severe test of the purity of the 

 electrolyte. With pure electrolytes the deposits in 

 this form are always crystalline and free from 

 striations. The efficiency of the porous cup as a 

 separator of the anode and cathode liquids is 

 shown by the fact that an impure solution may 

 be placed inside the porous cup without affecting 

 the deposit outside or if the deposit from a con- 

 taminated solution be compared with the deposit 

 from the same solution after filtering through a 

 porous cup it will be noted that the striations have 

 disappeared from the deposit. 



The small porous cup voltameter possesses many 

 advantages over the other forms. We find from a 

 long series of determinations two identical voltam- 

 eters of this type will agree to within one part in 

 100,000. 



