. Dental electro-therapeutics. used by him in actualpractice for the treatment of pyorrhoea alveolaris wereused for the experiment, which was performed as an oculardemonstration of the small amount of current strengthrequired to instantaneously produce a movement of ionsfrom soluble electrodes. To quote the experiment fromthe proceedings of the Roval Society of Medicine, vol. v,1912. I have here two glass tubes, each 6 cm. long and 1 diameter, open at both ends, these tubes are filled with CONDUCTION BY IONS 215 coagulated albumen. In one tube the albumen has beenmixed with a trace of fe
. Dental electro-therapeutics. used by him in actualpractice for the treatment of pyorrhoea alveolaris wereused for the experiment, which was performed as an oculardemonstration of the small amount of current strengthrequired to instantaneously produce a movement of ionsfrom soluble electrodes. To quote the experiment fromthe proceedings of the Roval Society of Medicine, vol. v,1912. I have here two glass tubes, each 6 cm. long and 1 diameter, open at both ends, these tubes are filled with CONDUCTION BY IONS 215 coagulated albumen. In one tube the albumen has beenmixed with a trace of ferricyanide of potassium, the othercontains pure albumen. The tubes are placed side by sidestanding on the small platform, which has a platinumelectrode connected by wire to the thumbscrew, to whichis attached the negative lead wire; the other ends are incontact with a similar electrode which is connected withthe other thumbscrew, to which is attached the positivelead wire. The albumen is the electrolyte, which, being Fig. 128. Ferrous and copper ions in albumen. white, readily shows the movement of ions as they takeplace. Two lengths of iron wire, each 2 cm. long and 1 , are placed one on each end of the glass tube con-taining the mixture of albumen and ferricyanide of potas-sium, passing along the side of the glass so that they arereadily seen, the ends of the wire are bent over the sidesof the glass and are in contact with the platinum similar arrangement is carried out with copper wire inthe other glass tube which contains pure albumen. The reason for mixing ferricyanide of potassium with 216 ELECTRO-THERAPEUTICS the albumen in the tube in which is placed the iron wire isthat ferrous ions are invisible, but when brought in con-tact with ferricyanide of potassium, Prussian blue is and copper are both soluble electrodes, and when acurrent of about 5 ma. is passed you can see ferrous ionsand copper ions migrate from the surface of the metals,the
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