304 Intelligence and Miscellaneous Articles. 



ments into a pan of water and hang up again. The space between 

 the elements being T ^ inch, will hold a drop of water which will 

 not evaporate for possibly an hour. Thus the battery is in opera- 

 tion in a minute, and is perfectly insulated by the glass and cement. 

 This is the form I have used ; but the strips might better be 

 soldered face to face along one edge, cut up and then opened. — 

 Silliman's American Journal, February 1887. 



ON THE GALVANIC POLARIZATION OF ALUMINIUM. 

 BY DR. F. STREINZ. 



Plates of aluminium were investigated by a method described in 

 Wiedemann's Annalen, vol. xxix. p. 181, and modified by opening 

 and closing the polarizing-current by a tuning-fork instead of by the 

 polarization-current itself. Phenomena were thereby observed 

 which were very surprising. 



The original difference of potential between amalgamated zinc in 

 a concentrated solution of zinc sulphate, and the bright metallic 

 aluminium plates of the voltameter, amounted to 0-32 volt. 



If, now, the latter were polarized, and first one and then the 

 other plate compared with the zinc plate at the electrometer, it 

 was found that the difference of potential of the plate charged with 

 oxygen increased within very wide limits with the electromotive 

 force of the polarizing-cell, while the plate charged with hydrogen 

 at small electromotive forces showed none, or only a very small 

 polarization ; but at considerable electromotive forces, a difference 

 of potential opposite in direction to ordinary hydrogen polarization. 



A few of the numbers found are collated in proof of this. For 

 the two polarizations (Zn/ Al + O and Zn /Al + H 2 ), fifteen minutes 

 after alternate closing and opening of the primary current by the 

 tuning-fork, there was found for the electromotive forces of 



Zn/Al+O. Zn/Al+H 2 . 



1 Daniell 1*12 volt. 0-31 volt. 



2 Daniells 1-94 „ 0-32 „ 



3 Daniells 2-81 „ 029 „ 



4 Daniells 3-31 „ 0-36 „ 



7 Daniells 5*52 „ 0-49 „ 



11 Daniells 7'50 „ 0-76 „ 



If the primary current was permanently open, the high values 

 for oxygen polarization at once fell considerably, while the values 

 for hydrogen polarization usually changed but little. It may still be 

 observed that the disengagement of gas at the aluminium elec- 

 trodes, even when the primary current has great electromotive 

 force, is very small compared with that observed in other metals. 

 The cause of this phenomenon is obviously to be sought in the 

 great opposing force of oxygen polarization. To confirm this, 

 measurements of the intensity in the primary current were made. 

 On this, and on the further results of the investigations, a report 

 will be made. — Kaiserl. Akad. cler Wiss. in Wien, December 16, 

 1886. 



