Apbil 10, 1908] 



SCIENCE 



567 



taining Distributed Capacity: Gael 



Kinsley, University of Chicago. 



In alternating current circuits, particu- 

 larly those approaching the condition of 

 resonance, the self-indu.ction, capacity and 

 resistance as used are frequently far from 

 correct. 



(1) The self-induction must include that 

 of the source. If a small transformer is 

 used its self-induction may be a consider- 

 able part of that of the circuit. (2) The 

 capacity must be measured with the same 

 conditions under which it is employed in 

 the circuit. (3) The resistance of the cir- 

 cuit is both the ohmic resistance and 

 the apparent resistance introduced by 

 hysteresis. The importance of each cor- 

 rection was discussed and illustrated. 



The use of periodic and aperiodic current 

 variations over artificial lines was studied 

 by means of the Braun tube. The condi- 

 tions which must be satisfied in working 

 over long lines were discussed. The paper 

 was illustrated with diagrams and lantern 

 slides. 



The Capacity of Paper Condensers and 

 Telephone Cables: Anthony Zeleny 

 and A. P. Andrevfs, University of Min- 

 nesota. 



The free-charge capacities of various 

 paper condensers and a telephone cable 

 were compared with their capacities as ob- 

 tained by the ordinary method where the 

 galvanometer remains connected during the 

 whole period of its throw (A. Zeleny, 

 Physical Review, 1906, Vol. 22, p. 65). 



The accuracy with which the free charge 

 can be determined is shown by discharge 

 curves which give the relation between the 

 quantity and the time of discharge. In 

 most cases, the free charge determinations 

 can be made to within one tenth of one 

 per cent., and the capacities as obtained 

 by the ordinary method are shown to be 

 from 2 to 300 per cent, greater than the 



free charge capacities, the amount of differ- 

 ence depending on the condenser. 



Errors are shown to exist in the present 

 methods of determining the specific capaci- 

 ties of dielectrics and in the resistance of 

 dielectrics as obtained by the loss-of-charge 

 method. 



A Hydrogen Peroxide Cell: H. T. Baenes 

 and G. W. Sheaeee, McGill University. 

 (Read by title.) 



Two papers have been presented before 

 the American Electrochemical Society by 

 one of the authors in conjunction with H. 

 M. Tory and G. H. Cole, where the results 

 of experiments on the effect of dissolved 

 gases in water on metal surfaces have been 

 given. In the second paper a cell was de- 

 scribed which consisted of electrodes of 

 aluminum and magnesium in a solution 

 of aluminum sulphate, to which some 

 hydrogen peroxide was added. Aluminum 

 metal behaves in a peculiar manner in 

 contact with dissolved air, or oxygen, and 

 becomes electronegative to a similar alumi- 

 num electrode in water free from dissolved 

 air. Magnesium does not show this effect : 

 hence a cell with the two metals for elec- 

 trodes has a comparatively large E.M.F. 

 developed between them when dissolved air 

 or oxygen is introduced. The effect is con- 

 siderably increased by adding hydrogen 

 peroxide. Acting on the suggestion of 

 Professor Bancroft, tests were applied to 

 the water in which clean aluminum had 

 stood for a few hours, and a measurable 

 quantity of hydrogen peroxide was de- 

 tected. This was developed from the ac- 

 tion of the dissolved oxygen on the alumi- 

 num, probably according to the following 

 reaction, also suggested by Bancroft: 



2A1 -^ 6H2O 4- 60 = AL ( OH ) „ + 3H,0j. 



The amount of yield of the peroxide was 

 considerably increased in several ways. 

 Without dissolved air no trace of peroxide 



