TO Scientific Intelligence. 



From these results the conclusion is reached, since the rapidity 

 of the reaction diminishes rapidly with the pressure of the gas in 

 the apparatus, that solid carbon does not reduce oxide of iron, at 

 least at 050° C, although it has been previously supposed that this 

 reduction commences at 450°. — Comptes Hendus, cli, 644. 



H. L. W. 



3. Action of Light upon an Electric Cell. — H. Pelabon has 

 observed that if two rods, one of pure antimony and the other 

 of an alloy of antimony and selenium, are plunged into a hydro- 

 chloric acid solution of antimony trichloride, a cell is obtained in 

 which the pure antimony acts as the negative pole. This cell 

 has curious properties. If it is kept in darkness its electromotive 

 force, in open circuit, attains a constant value in a few days, 

 provided that the temperature remains constant. Upon suddenly 

 illuminating the positive pole, the electromotive force, originally 

 E , increases at once to a much higher value, E,, and then, the 

 illumination being maintained, it diminishes, and in the course of 

 about 20 minutes reaches the original value E , which remains 

 constant under these conditions. Then when the illumination 

 is cut off the electromotive force diminishes to a value E a , when 

 it, increases slowly and in about an hour reaches the original value 

 E„, which is maintained continuously in darkness. The same 

 phenomenon is observed, whatever may be the proportion of 

 selenium in the positive electrode, but alloys low in selenium 

 appear to be the most sensitive. Tellurium and sulphur when 

 alloyed with antimony do not give this behavior. The nature of 

 the metal influences enormous^ the delicacy of this phenomenon. 

 Almost all the metals with their selenides give cells which are 

 sensitive to light. — Comptes Hendus, cli, 041. h. l. w. 



4. Sterilization of Large Quantities of Water by Ultra-violet 

 Rays. — Helbronner and Recklinghausen have devised an 

 apparatus for the treatment of water on a large scale with the 

 rays of the quartz-mercury-vapor lamp. The lamp is placed in 

 a box, three sides of which are composed of quartz plates, and the 

 current of water in the apparatus flows against each of these 

 plates in succession. In this way more than three-quarters of 

 the rays emitted by the lamp are utilized. It was found that the 

 transparency of the treated water is of the greatest importance 

 and that it is desirable to filter the water to clarify it before the 

 treatment. The authors have installed a practical apparatus 

 treating about 160,000 gallons per day, which gave most satisfac- 

 tory results for a period of six weeks. Before passing through the 

 apparatus the water contained from 30 to 300 germs per cubic 

 centimeter, including 50 to 1000 of bacillus coli per liter. After 

 the treatment the water contained an average of one germ per 

 cubic centimeter, and not a single bacillus coli. The lamp 

 employed was of the Westinghouse-Cooper-Hewitt type of 220 

 volts and 3 amperes, so that the electricity employed amounted 

 only to about luO watts-hour per 1000 gallons. — Comptes Hen- 

 dus, cli, 677. h. l. w. 



