420 CURREET TOPICS. [J. F. I.

A Continuous Process for Electrolytic Regeneration of Chromic Acid is described by RALPH H. MCKEE and SHOO TZE LEO of Columbia University in the Jourllal of Isdustrial and Engi- neering Chemistry, 1920, xii, 16-26. The cell contains a porous diaphragm and lead electrodes. The fresh waste liquor containing chromic salts is fed directly into the bottom of the rectangular cell at one end of the inner or cathode chamber and overflovs through an orifice at the other end of the same chamber into the outer or anode chamber, in which the level of the electrolyte is kept slightly lower. The finished product is drawn off at the opposite end of the anode chamber by a siphon or overflow. The best results were ob- tained when the current density was from 0.5 to 2 amperes per square decimeter of anode surface. The yield was best at room tem- perature, poorer at both 10~ C. and 55” C. A decrease in the size of the cathode for the same anode did not make any appreciable difference. The waste liquor was passed through a sand fillter 2 inches deep before entering the cell. Further preliminary treatment was unnecessary ; the electric current destroyed all organic com- pounds present in the liquor. The chromic acid content of the prod- uct was up to commercial standard. Approximately 3 kilowatt hours of electric energy were required for each pound of chromic acid regenerated. The saving of sulphuric acid, which is also re- generated in the process without additional cost, amounted to almost as much as the cost of the electric energy required to regenerate the chromic acid. J. S. H.

Power from the Sun. X. A. CAMPBELL SWINTON. (La LVatawc, December 18, IgIg.)-The power derivable from the sunlight inci- dent on the earth amounts to about 4,ooo,ooo horsepower per square mile in certain latitudes, or in Great Britain to 1000 horsepower per acre during daylight. The author has Ilittle hope for utilizing much of this incident power by the heat engine or by processes of vegetable growth. Solar radiation consists of electro-magnetic waves similar to the waves employed in wireless telegraphy, except that the latter are vastly longer. By thermionic or crystal rectifiers it is possible to get uni-directional currents of electricity from the waves of wireless telegraphy. Mr. Swinton raises the question whether by the use of suitable devices the shorter waves of the solar radiation cannot be made likewise to give rise to electric currents.

G. F. S.