Chemical Science. 429 



even after the separation of the two electric fluids has happened, 

 just as occurs with two voltaic piles. The two particles would 

 approximate and even come into perfect contact were it not for the 

 repulsive power of heat which keeps them separate, and prevents 

 the neutralization of their electricities. — Jahrb. der Phys, — Dull* 

 Univ. A. X. 150. 



2. Chemical Powers of Magjietwn. — The following experiment 

 is by the Abbe Rendu. If a bent glass tube be filled with the 

 tincture of red cabbage and two iron wires suspended to the poles 

 of a magnet be immersed in the liquid in the two branches, the 

 tincture will, in a quarter of an hour, become blue or of a deep 

 green * in both branches of the tube, although the magnetism of 

 the two wires must be of different kinds. The same result is pro- 

 duced if well tempered and polished steel needles be used in place 

 of the wires. If one wire be removed, the effect takes place 

 only in the other branch of the tube where the wire remains. The 

 same results occur if the wires are not in contact with a magnet ; 

 but being then cleaned they are found to have become magnetic. 

 Tincture of litmus undergoes similar changes, but far more slowly, 

 and the colour becomes green only in the leg containing the 

 north wire. 



M. Biot considered that the oxidation of the wires might in 

 these cases produce the ordinary effects of a voltaic current, but 

 that as magnetism exerted its influence notwithstanding the pre- 

 sence of interposed bodies, he advised M. Rendu to separate his 

 wires from the tincture by small glass tubes closed at their lower 

 extremities. In this case even, according to M. Rendu, the same 

 phenomena were produced, but much more slowly. The tincture 

 of red cabbage, however, became perfectly green in two days. — 

 Mem. de Savoie. — Bull. Univ. A. x. 196. 



3. Effect of Magnetism on the Precipitation of Silver. — ^The 

 following very shigular results (if correctly reported, and there 

 seems to be no reason to doubt them in that respect) strikingly 

 illustrate the influence exerted by magnetism over the precipitation 

 of silver. All of them were made by Professor Muschman, and 

 some so early as 1817. A glass syphon, half an inch in diameter 

 and fixed with its angle downwards, had mercury poured in so as to 

 cover the lower part, but not prevent free communication between 

 the two legs, and then a solution of nitrate of silver of specific gravity 

 1.109 was poured in so as partly to fill both legs. The syphon was 

 placed accidentally in the plane of the magnetic meridian ; in a 

 few minutes the silver was precipitated, and, to the surprise of the 

 observer, more abundantly and with more brilliancy in the leg 

 towards the north than in the other. 



* The resemblance of salts of iron to alkaline solutions in their effects on vege- 

 table colours has been noticed long ago, and must not be forgotten here.— See 

 ^uart. Journal, vol. xiii. p, 315, 



OCT.— DEC, 182S. 2 G 



