A manual of practical medical electricity : the Röntgen rays and Finsen light . k, is not nearly soimportant to us as is durability without constant atten-tion. The Grove and Bunsen Cells. {a) The electrolyte is a strong solution of sulphuricacid. {b) The positive plate is a cylinder of zinc. (c) The negative plate is contained in a porous potthree - parts filled with strong nitric acid, and is ofplatinum foil in the Grove, and a stick of carbon in theJBunsen. (d) The depolarizer is the nitric acid. The E. M. F. is about two volts, and the internal resist-ance about 02 ohm. The current is ther
A manual of practical medical electricity : the Röntgen rays and Finsen light . k, is not nearly soimportant to us as is durability without constant atten-tion. The Grove and Bunsen Cells. {a) The electrolyte is a strong solution of sulphuricacid. {b) The positive plate is a cylinder of zinc. (c) The negative plate is contained in a porous potthree - parts filled with strong nitric acid, and is ofplatinum foil in the Grove, and a stick of carbon in theJBunsen. (d) The depolarizer is the nitric acid. The E. M. F. is about two volts, and the internal resist-ance about 02 ohm. The current is therefore very strongon short circuit, for 2 volts - , =10 ohm Forms of Primary Cells 51 During action, zinc sulphate is formed at the expense ofthe zinc and sulphuric acid, while the liberated hydrogenis oxidized by the nitric acid to form water and nitric per-oxide, which escapes in reddish fumes. In the figure (Fig. 26) the outer vessel is seen to be ofglass ; this contains the sulphuric acid, and acleft, heavy,well-amalgamated cylinder of zinc. The porous pot con-. za\j^! Fig. 26.—BuNSEN Cell. taining the nitric acid and a rod of carbon stands in thecentre. But little need be said about this form of cell here. Itwill furnish a very strong current, which will remainconstant for two or three hours ; but the strong acids,noxious fumes, and want of durability, unless it be dis-mounted after every use, entirely preclude it from a per-manent installation. Occasionally it is still set up in ahospital for an electrolysis, or to light a lamp or heat a 4—2 52 A Manual of Practical Medical Electricity cautery ; it is of use also in charging an the invention of the dynamo, it was in frequentdemand to light an arc lamp, some fifty cells being coupledtogether in series. The subject of batteries will be postponed until E. M. F.,current-strength, resistance, and faradic electricity havebeen discussed. CHAPTER V ELECTROMOTIVE FORCE We have already seen that di
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