Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . s deposited should be perfectly clean, and freefrom a film of air, that it may adhere ; and the metalshould be thrown down with sufficient energy toprevent any local action with the mould. The arti-cle to be silvered or gilded may in some cases becleaned by a solution of potash; but the deposit ismore certain to adhere if the surface is rubbed witha little rottenstone when first placed in the metallicsolution, and connected with the battery. When-ever
Davis's manual of magnetism : including galvanism, magnetism, electro-magnetism, electro-dynamics, magneto-electricity, and thermo-electricity . s deposited should be perfectly clean, and freefrom a film of air, that it may adhere ; and the metalshould be thrown down with sufficient energy toprevent any local action with the mould. The arti-cle to be silvered or gilded may in some cases becleaned by a solution of potash; but the deposit ismore certain to adhere if the surface is rubbed witha little rottenstone when first placed in the metallicsolution, and connected with the battery. When-ever, during the process, the deposit becomes discol-ored or rough, the negative plate should be takenout, and brushed with a little whiting and soap andwater. The thickness of the coating of gold andsilver is proportional to the time occupied by the de-position and the amount of electricity which the same amount of electricity, 32 grains ofcopper, 108 grains of silver, and 99 grains of gold,are deposited, these being the chemical equivalentsof those metals. 104. If a small object, such as a dial of a watch, 6* 6b D AVIS S MANU be placed in a solution of cyanide of silver or gold ina capsule, the metals will be thrown down upon itFig. 37. in a very satisfactory manner, if a small slip of zinc be placed in con-tact with it, as represented by Z inFig. 37, and the whole be heatedby a spirit-lamp. It is necessarythat there should be rather morecyanide of potassium in the solutionthan in that for the ordinary dial of the watch itself becomeshere one plate of the battery, and theslip of zinc the other. The zinc isdissolved by the solution ; but by the law regulatingthe deposit of alloys, only gold is thrown down bythe feeble current which is excited. 105. When a solution of acetate of lead is de-composed, a very beautiful result ensues at the posi-tive pole. To exhibit this, a large polished metallicsurface is connected with the positive wire in the solu-tion,
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectmagnetism, bookyear18
