A manual of practical medical electricity : the Röntgen rays and Finsen light . Fig. 18.—Bichromate Battery. required, because the zinc is slowly dissolved, even whenthe circuit is not completed. Depolarization is very effective at first, but soon failsunless the liquid be constantly agitated. Thus, if thecurrent from the bottle cell seem to fail, it can bestrengthened by shaking the bottle, or by raising andlowering the zinc. Stohrers battery, though formerly intended to be usedwith dilute sulphuric acid, like a Smee, is now practicallymade up of a number of ordinary bichromate cells, witha c
A manual of practical medical electricity : the Röntgen rays and Finsen light . Fig. 18.—Bichromate Battery. required, because the zinc is slowly dissolved, even whenthe circuit is not completed. Depolarization is very effective at first, but soon failsunless the liquid be constantly agitated. Thus, if thecurrent from the bottle cell seem to fail, it can bestrengthened by shaking the bottle, or by raising andlowering the zinc. Stohrers battery, though formerly intended to be usedwith dilute sulphuric acid, like a Smee, is now practicallymade up of a number of ordinary bichromate cells, witha convenient lifting arrangement for the vessels. Forms of Primary Cells 41 The Silver Chloride Cell. Of this there are various forms, both dry and Kquid. (a) The electrolyte may be a solution of sal-ammoniac,chloride of zinc, or potash. (b) The positive element is zinc. (c) The negative element is silver, (d) The depolarizer is chloride of silver. The E. M. F. varies according to the form from about. Fig. 19.—Silver Chloride Cell. •9 volt to 17 volts ; the internal resistance in the portablesize from about 3 ohm to 4 ohms. During action the silver chloride absorbs the hydrogen,producing silver and hydrochloric acid. The cells are usually put up in glass or vulcanite vessels,hermetically closed by an ebonite lid and indiarubberwasher. A piece of silver wire forms the negative element,which is surrounded by chloride of silver in a granular 42 A Manual of Practical Medical Electricity form contained in a muslin bag (Fig. 19). The elementsare prevented from touching by a piece of indiarubber orglass. In the dry forms, the exciting solution is either replacedby a piece of sponge or bibulous paper, which is moistenedwith the excitant and then fixed between the plates(these being kept close together by indiarubber rings),or it is mixed with corn-starch to form a sort of blanc-mange. It is difficult to know what position to give this the latest form it is claimed that its
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