Chemistry and Physics. 235 



density of liquid oxygen and of ethylene. Both gases were liquefied 

 in U-tubes immersed in liquid air. Two experiments with differ 

 ent glass rods, gave for oxygen at the boiling point of liquid air (be- 

 tween — 183° and —188°) a density of 1*105-1-108; these values 

 becoming 1-110 and 1*113 when the correction for the change in 

 volume of the glass is applied. Olszewski's value at —181*4°, the 

 boiling point of oxygen, was somewhat higher, 1*110 to 1*137. 

 On passing ethylene gas into a tube immersed in liquid air in a 

 Dewar globe a crystalline mass of solid ethylene is at once ob- 

 tained, whose melting point was found to be —169°, and its 

 boiling point —105 -4° at 760 mm pressure. The density of the 

 liquid ethylene at —169° was found to be 0-6585 and at —105*4°, 

 0-5710. Methane made from sodium acetate and barium oxide 

 gave variable results, probably from the presence of hydrogen 

 and perhaps of ethylene. — Per. Perl. Chem. Ges., xxxii, 46, Jan- 

 uary, 1899. G. F. B. 



2. On Semi- Permeable Membranes. — Experiments which have 

 been made by Mijers have led him to differ from the opinion of 

 Ostwald that semi-permeable membranes are not only conductors 

 like metals but are also "ion sieves." He calls attention to the 

 fact that the copper which is deposited on semi-permeable mem- 

 branes possesses the nature of a spongy mass rather than a 

 coherent one. If a glass cylinder be closed by a membrane of 

 copper ferrocyanide on parchment paper, and be filled with nor- 

 mal solution of copper sulphate, and then placed in an electrolyz- 

 ing vessel containing the same solution, the current from two 

 Bunsen cells being passed through it, it is found that no copper 

 is deposited on the membrane during the first half hour, a deposit 

 taking place only when the liquid in the cylinder has become 

 nearly colorless. On weighing the cathode, which is placed in 

 the cylinder closed by the membrane, both before and after the 

 experiment, it is observed that the amount of the deposited cop- 

 per is in excess, by a considerable amount, of that which was 

 previously contained in the solution in the cylinder, showing that 

 copper must have passed through the membrane. Placing a pla- 

 tinum cathode in acidulated water in a similar cylinder closed by 

 a membrane, and putting this in an electrolytic vessel containing 

 copper sulphate solution, metallic copper is deposited in a few 

 minutes on the cathode ; and after four hours the amount of this 

 copper is more than a hundred times that contained in the precip- 

 itated copper ferrocyanide on the membrane, which retains its 

 color and is not acted on by the acid. The author's experiments 

 seem to show that semi-permeable membranes are conductors 

 differing entirely from metals. Thus if, in a copper sulphate 

 electrolyzing vessel the anode and cathode are separated by a 

 semi-permeable membrane held between two rings of ebonite, and 

 by a sheet of platinum of exactly the same size as the membrane, 

 no metal is deposited on the membrane when the current passes, 

 the deposit taking place on the platinum near the center, the 

 margin being protected by the ebonite. — Rev. Trav. Chim., xvii, 

 177, 1898; J. Chem. Soc, lxxiv (ii), 505, November, 1898. 



G. F. B. 



Am. Jour. Sci.— Fourth Series, Yol. VII, No. 39.— March, 1899. 

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