ELECTRICITY. 



gftfl 



tinctly strong N. and S. polos, produced by tbe 

 8. a:i - of the block. 



-Place tho wire reversed on tbo 



Mock, i. o., lay tbe N. polo of tbe wire on tho 



:o of tho block, and bammor as before. 



1 again by tbe noodle, tbo wire exhibits 



..lea reversed. 



I-.'j-ft. ''.. Lay the wire as in Expt. 1, and 



ner; the original polarity is restored. Fi- 



nully, by changing tho position of tho wire, 



j-olo maybe cbaugod and rechangod as 



loii'.j :is tbe wire lasts. 



Tii oso experiments would seem to represent 

 well tho magnetizing action of tho earth. Tho 

 Mock personates the earth with its magnetism, 

 which is not less comparatively than that of 

 the cast-iron. Were the wire to remain for a 

 considerable time lying on tho block, it would 

 be magnetized. The hammering effects quietly, 

 in tho whole wire, that molecular disturbance 

 which is slowly and piece by piece produced 

 in groat masses of iron standing on the earth. 



Gases in Metals deposited by Electricity. 

 M. 15. Lenz, of St. Petersburg, has observed 

 that iron, when thrown down from a mixed 

 solution of ferrous sulphate and sulphate of 

 magnesia, kept neutral by tbe presence of mag- 

 noaian carbonate, is very hard and brittle. 

 When heated to redness, however, it becomes 

 softer and flexible, and la the calcination much 

 gas is evolved for the most part hydrogen, 

 borne is carbonic acid, resulting from the neu- 

 tralization of the electrolyte by carbonate of 

 magnesia ; and some is nitrogen, not accounted 

 for. . Layers of iron of different thicknesses 

 absorb gas very unequally. The thinnest layer 

 yielded 18.5 times its volume of gas; one of 

 twice that thickness gave out only half that 

 volume ; and another three times as thick 

 yielded only one-third as much. A piece of 

 iron, from which the gas had been driven by 

 heat, and placed in water, was found to de- 

 compose the water and absorb hydrogen. Cop- 

 per, deposited by electrolysis, also occludes 

 gas, of which 77 per cent, is hydrogen ; but 

 what the other gases are M. Lenz does not say. 



Electro- Metallurgy. M. T. Chutaux, of 

 Paris, claims an improvement on the common 

 methods of tho electro-deposition of metals, 

 by the following process : He keeps tho solu- 

 tion agitated by power supplied' from the 

 electric battery, which serves to do the plat- 

 ing thus : a revolving-shaft, with a helix at its 

 lower end, is placed vertically in tho middle 

 of the receptacle containing the solution. Its 

 upper end, crossing a support composed of iso- 

 lating material resting on tho receptacle, is at- 

 tached, by an endless band passing over grooved 

 pulleys, to the shaft of a fly-wheel, operated by 

 a connecting-rod attached to an armature, acted 

 upon by tho electro-magnet attached to tho 

 battery. The rotation gjven to the shaft is 

 transmitted to the helix, an ascending current 

 is established in the middle of the receptacle, 

 ami a descending current toward its sides, in 

 such a manner that all tho parts of tho objects 



operated upon arc in a continual contact with 

 a liquid of coual richness throughout, and tho 

 metal is thus deposited regularly and uniformly. 



Tho Journal of Applied Chemutry mentions 

 successful experiments of E. Klein, a Russian 

 mining-engineer, in tho electro-deposition of 

 iron, suitable for printing, and combining 

 cheapness with durability, respects in which 

 copper stereotypes are wanting. Tho process 

 is not described, but its efficacy is rc[>rtr<l t 

 depend almost altogether on the solubility of 

 tho iron anode, which Klein has succeeded in 

 increasing by a peculiar composition. It wiw 

 found that, on enlarging the surface of tho nn- 

 pde beyond a certain point, tho result was not 

 improved. According to another authority, 

 tho material used to furnish the iron is a di- 

 lute solution of the double sulphite of tho 

 protoxide of iron with sulphate of potash, soda, 

 or magnesia, and tho apparatus, a battery of 

 low power, usually two small Smee's elements. 

 It is said that the iron thus deposited is of 

 groat beauty, has a beautiful lustre and a silky 

 texture. No exact experiments have as yet 

 been made on its tensile strength or conduc- 

 tivity. Faithful copies of examples of mcdi- 

 fflval art of extreme intricacy have already 

 been produced by this means, tho moulds used 

 being of gutta-percha, or, in fact, of any ma- 

 terial commonly used by tho electro-metal- 

 lurgist for such purposes. Tho process has 

 also been applied to the production of stereo- 

 types, and to a number of other purposes. 



The latest improvements in Mr. W. IT. 

 Walenn's invention to make electro-depositions 

 of brass are thus described by the author in a 

 paper read before the British Association : 



Ordinarily, n solution containing tho cyanides of 

 copper and zinc, respectively, dissolved in a "sol- 

 vent solution " consisting of a mixture of potassio 

 cyanide with a salt of ammonium, is employed to de- 

 posit brass. This solution, however, evolves hydro- 

 pen copiously, and is only workable by means of two 

 Grove's cells. The author finds that the evolution 

 of gas may be either totally stopped, or much less- 

 ened, by dissolving as much of the metallic cyanidea 

 as tho solution will take up, and then further charg- 

 ing the solution with the copper and zinc oxides. 

 The evolution of gas may be totally stopped by tho 

 further addition of cupric ammonide, which may pos- 

 sibly carry the combined oxygen to the cathode. 



That is to say. before decomposition or chemical 

 reaction takes place, tho whole of the cuprio am- 

 monide, together with tho eliminated hydrogen, goes 

 to the cathode ; after tho decomposition or chemical 

 reaction has taken place, metallic copper is deposited, 

 ammonia is in solution, and water is formed. 



In treating the ordinary cyanide copper solution 

 for the prevention of tho evolution of hydrogen, the 

 zinc cyanides or oxides, mentioned in tho instance 

 of tho brass solution, are left out. 



When tho evolution of hydrogen has been stopped, 

 a single Smoe's cell is sufficient to deposit the alloy ; 

 but, in practice, a single Grove's cell, or equivalent 

 magneto-electric power, is employed, in order to 

 shorten the time of immersion in the electro-coaling 

 bath. 



The author prefers to use potassio cyanide and 

 neutral ammonium tartrate, ^yhen mixed with water, 

 to form the solvent solution for either brass or copper. 

 The quality of brass (yellow or red) depends upon 

 the heat of tho solution. 



