48. A much more convenient and effectual arrangement for chemical decompositions by common electricity is the following. Upon a glass plate, fig. 4, placed over, but raised above a piece of white paper, so that shadows may not interfere, put two pieces of tinfoil a, b; connect one of these by an insulated
Fig. 4.
wire c, or wire and string (37), with the machine, and the other g, with the discharging train (28) or the negative conductor; provide two pieces of fine platina wire, bent as in fig. 5, so that the part d, f shall be nearly upright, whilst the whole is resting on the three bearing points p', c, f; place these as in fig. 4; the points p, n then become the decomposing poles. In this way surfaces of contact, as minute as possible, can be obtained at pleasure, and the connection can be broken or
Fig. 5.
renewed in a moment, and the substances acted upon examined with the utmost facility.
49. A coarse line was made on the glass with solution of sulphate of copper, and the terminations p and n put into it; the foil a was connected with the positive conductor of the machine by wire and wet string, so that no sparks passed: twenty turns of the machine caused the precipitation of so much copper on the end n, that it looked like copper wire; no apparent change took place at p.
50. A mixture of equal parts of muriatic acid and water was rendered deep blue by sulphate of indigo, and a large drop put on the glass, fig. 4, so that p and n were immersed at opposite sides: a single turn of the machine showed bleaching effects round p, from evolved chlorine. After twenty revolutions no effect of the kind was visible at n, but so much chlorine
