248 Mr. Shelford Bidwell on the 



evidently only to transferred particles of selenide. The other 

 papers had received stains which differed greatly in appearance 

 according as they were upon the anode or the kathode. 



On the anode papers the stains were scarlet, and I satisfied 

 myself that they were beyond doubt due to red amorphous 

 Se. For (1) stains of a precisely similar hue and character 

 were obtained by electrolysing a solution of selenious oxide 

 contained in a pad of filter-paper, though of course in this 

 case the stain appeared upon the kathode. (2) The stains 

 turned dark brown when heated. (3) They were not affected 

 by cold hydrochloric acid, as red oxide of copper would have 

 been. (4) Nor by sulphuric acid. (5) Nor (unless very 

 slowly) by cold nitric acid. (6) Hot nitric acid quickly 

 dissipated them. (7) So also did a mixture of cold nitric and 

 hydrochloric acids. (8) The red stuff could be volatilized at 

 a temperature below that at which the paper was scorched. 



On the kathode papers the stains were of a dark brown, 

 nearly black, shade, surrounded by small irregular patches of 

 green, blue, and orange. The dark-brown stuff acquired a 

 metallic copper-coloured lustre when burnished, which is 

 sufficient proof that it consisted, largely at all events, of finely 

 divided metallic copper. It was ascertained that if a little of 

 the selenide itself were finely powdered, rubbed into moist 

 paper and dried, no such metallic appearance was produced 

 by burnishing. 



The experiment was repeated several times with variations 

 in the details : e. g. in one case the selenide was fused with an 

 excess of Se, in another with an excess of Cu. But it was 

 invariably found that red stains were formed at the anode, 

 and almost invariably traces of metallic copper appeared at 

 the kathode. 



This experiment naturally led me to try to obtain electri- 

 cally liberated selenium in larger and measurable quantities. 



Exp. 22. — Some selenide of copper was prepared by heat- 

 ing together 126 parts of shredded copper-foil and 79 of 

 crushed Se in a closed crucible to bright redness. The 

 product was an iron-grey, cindery-looking mass. 



A fragment of this was held in a brass clip, and the lower 

 portion of it dipped into a beaker of water opposite a strip of 

 Pt foil. The selenide was joined to the negative pole of the 

 battery, the Pt to the positive : thus the water was made the 

 anode in relation to the selenide. A current of 0*025 ampere 

 was passed for half an hour. In a few minutes after starting, 

 the water had become scarlet and quite opaque with suspended 

 red Se. Unfortunately, however, the selenide was very 

 friable, and numerous small particles were detached from its 



