C. GENERAL PHYSICS. 1V7 



sulphuric acid due to the oxidation of the sulphur used in 

 vulcanizing the rubber. It now appears that the production 

 of ozone by electric sparks is not, as Wright supposed, the 

 sole cause of the phenomenon. A plate of ebonite polished 

 on both sides was sawed into four strips, each 52 mm. by 22 

 mm. by 8.5 mm., exposing therefore about 3500 sq. mm. of 

 surface. One half of each piece was varnished with shellac. 

 Two of these pieces were placed in wide test-tubes plugged 

 with cotton-wool, and the other two were sealed hermetical- 

 ly in similar tubes. One of the sealed tubes and one plug- 

 ged with cotton-wool were placed in a dark drawer, and the 

 other pair exposed to light in the laboratory, and during the 

 latter part of the experiment to direct sunlight. The ex- 

 periment was commenced on December 26, 1874, and after 

 some time minute drops of liquid were perceived on the 

 ebonite exposed to light and air, the remaining three pieces 

 retaining their original appearance. Between September 1st 

 and 21st of this year the sealed tube exposed to light was 

 accidentally broken, so that for a period of less than three 

 weeks the ebonite in it was exposed to both light and air. 

 On September 21st the tubes were opened, the ebonite wash- 

 ed with water, and the amount of acid determined by stand- 

 ard solution of caustic soda. No trace of acid could be de- 

 tected on either of the pieces of ebonite which had been kept in 

 the dark. On the one which had been exposed to light in the 

 closed tube 0.343 milligrammes of sulphuric acid was found, 

 and on that exposed to light and air 2.646 milligrammes. In 

 confirmation of these results, the author notices an excellent 

 instance of the action of light on vulcanite which occurred 

 in the laboratory of Warren De la Rue. An apparatus with 

 an ebonite base with three adiustino^ screws was standing- at 

 some distance from a window. The surface of the plate was 

 covered with a fine dew of an acid liquid, except at the parts 

 where the shadows of the heads of the screws fell. The sur- 

 face at these places completely retained its original polish. 

 12 ^1, Oc^o^er 12, 1876, 525. 



AMALGAMATION OP IROX. 



In a paper read before the American Chemical Society, 

 Casamajor describes a new method of amalgamating iron, 

 which promises to render this metal useful for many novel 



112 



