Intelligence and Miscellaneous Articles. 151 



cancelled. Iu Table XXI., Section 6, the ratio Jc/(3 for C0 2 is 

 given as 4 instead of 2-5, the logarithm having been copied in place 

 of the number. 



Tours obediently, 

 Melbourne, April 1893. William Sutherland. 



ON A REMARKABLE PHENOMENON OF OXIDATION OF PURE 

 ALUMINIUM WHEN IN CONTACT WITH MERCURY. BY E. O. 

 ERDMANN. 



As soon as the two metals are in actual contact, snow-white 

 filiform or straw- shaped formations result, growing from the point 

 of contact of the two metals, which in a few minutes acquire a 

 length of 2 to 3 centim. Under the microscope they appear as 

 tube-shaped or plate-shaped veils, of extreme delicacy and per- 

 fectly amorphous. If they are detached by tapping or shaking 

 they look like lint. Chemical investigation shows that they consist 

 of pure aluminium hydrate. 



It is immaterial for the formation of this oxide whether the 

 contact between the metals is effected by rubbing, or whether the 

 surfaces are purified with hydrochloric acid or caustic soda, and 

 subsequent washing with much water and drying with blotting- 

 paper. 



The cause of this peculiar oxidation might be sought for in : — 



(1) The formation of an easily oxidizable amalgam of aluminium, 

 which always forms at the surface of contact in the degree in 

 which aluminium oxidizes in moist air. 



(2) The electrolytic decomposition of a thin layer of water, 

 which is condensed on the surfaces of the two metals which form 

 the element. 



(3) That the highly positive aluminium by contact with mercury 

 acquires a greater affinity for oxygen, in the same manner as, 

 according to Magnus, iron-filings do when hanging to a magnet. — 

 Physical Society of Berlin, November 18, 1892 ; from Wiedemann's 

 Annalen, No. 1, 1893. 



ON THE PROCESSES WHICH TAKE PLACE AT THE BOUNDARY 

 BETWEEN TWO SOLUTIONS OF DIFFERENT CONCENTRATION 

 WHEN A CURRENT IS PASSED. BY GEORGE H. ZAHN. 



The results of these experiments are stated by the author as 

 follows. Besides the well-known formation of hydroxides of 

 magnesium, calcium, and copper above the boundary of a dilute 

 solution over a concentrated one of the same salt when an elec- 

 trical current passes from the concentrated to the dilute solution, 

 it is possible, when the concentrations are very different, to observe 

 the formation of a solid with barium, strontium, aluminium, iron, 

 manganese, and zinc in combination with several acids. Silver 

 does not exhibit such a behaviour. In each case, even with silver, 

 and with the salts of potassium and of sodium, which form readily 



