218 ELECTRO-METALLURGY 



permanent magnets, and exposes thorn to the most favourable action of these poles. 

 The number of coils and magnets varies in proportion to the work required. By this 

 arrangement, not only does each coil pass under the influence of many magnets', but 

 each magnet acts successively on many coils ; and a proportionate supply of electri- 

 city is the result. 



ELECTRO-DEPOSITION OF IRON. This has been often attempted, without much 

 success until recently. A process has now been discovered which answers admirably. 



This new process has been perfected by M. Eugene Klein, who is at the head of the 

 chemical department in the Imperial State paper manufactory in St. Petersburg. 

 Many difficulties have arisen and have been successfully surmounted in developing 

 this process to its present practical issue. Attempts were made to effect the object so 

 far back as tho year 1846, but which were unsuccessful, and it was about twenty 

 years before the problem was definitely solved. The importance and reality of the 

 progress, however, are now unquestionable, and an extended knowledge of the process 

 must inevitably lead to its general adoption. At the present time we believe its 

 application is confined to the Kussian Imperial State paper works, where it has been 

 in active operation for some time, the iron plates replacing those of copper for bank- 

 note printing and for other similar purposes. The application of tho invention, how- 

 ever, extends to all the other branches of the art of electrotyping. 



From a paper upon the present subject, read by the late Prof. Jacobi before tho Aca- 

 demy of Sciences in Eussia, in 1868, it appears that in the previous year M. Feuquieres 

 sent to the Paris Exhibition some specimens of iron electrotype which presented a fair 

 appearance as regarded surface, but still were inferior to those produced by M. Klein 

 in the year following. M. Feuquieres does not appear to have published tho process 

 by which he obtained his results, and he moreover only spoke of it with the greatest 

 reserve. Professor Jacobi, however, states, on the authority of Professor Varrentrapp 

 of Brunswick, that the process and the bath employed differ essentially from those of 

 M. Klein, whose results may be considered as being perfectly independent. 



Keferring to the process of electrotyping in iron, Professor Jacobi observes that tho 

 good quality of the iron deposit depends principally upon the greater solubility of 

 tho anode. The augmentation of its surface not having produced the desired effect, 

 M. Klein conceived the idea of combining the anode of iron with another of copper. 

 Tho Professor varied this combination by replacing the copper with horn-charcoal, which 

 gave more powerful results. The effects of this combination wero thus rendered com- 

 plete, the negative metal combined with the iron in the same bath formed a duplicate 

 layer, which worked as a cathode opposite the iron, and as an anode by its combination 

 with the copper-wire, or the positive pole of the pile which furnished the principal 

 current. The surface of this electrode consequently disengaged hydrogen and oxygen 

 simultaneously, which combined in the proportions which form water. Tho surplus 

 hydrogen freely disengaged itself, or produced a polarisation of tho electrotype. If, 

 observes the Professor, the oxygen is most abundant, and if the electrotype consisted 

 of an inoxidisable substance, such as horn-charcoal, it would also have disengaged gas, 

 and have given a feeble polarisation. If, however, the electrotype is oxidisable like 

 copper, it will be oxidised and dissolved. By immersing a galvanometer in tho 

 circuit, Professor Jacobi has observed the deviation of tho needle diminish by degrees 

 whilst the current was very feeble, and it became perfectly still after tho force of tho 

 current had been increased to a certain degree. At length, passing that degree, tho 

 Professor noted that the deviation again became inconstant. By means of the galva- 

 nometer, therefore, it becomes easy to so regulate tho current as to disengage neither 

 tho oxygen nor the hydrogen from the cathode. 



So far Professor Jacobi. Turning now to a letter from M. Klein, which was 

 placed before the Kussian Academy of Sciences in 1868, we have recorded tho methods 

 employed by him in tho production of iron electrotype. M. Klein saw M. Feuquieros' 

 specimens at the Paris Exhibition, and, encouraged by Professor Jacobi, he, on his 

 return to St. Petersburg in October 1867, renewed his attempts to electrotype in 

 iron. The scientific interest which attached to tho new development, and tho emi- 

 nently useful applications of which ho saw it was susceptible, especially in the 

 departments of engraving and printing, stimulated M. Klein, and in tho early part of 

 1868 he had accomplished his object. The medals produced in the early part of M. 

 Klein's researches showed, on their reverse, porosities and deep hollows which pene- 

 trated nearly through tho thickness of tho deposit. These cavities wore also observ- 

 able in great numbers in tho productions of M. Fouquieres. In M. Klein's later 

 specimens these singular cavities which probably proceeded from bubbles of gas 

 entirely disappeared, and thoir reverses are no way inferior to those of. copper speci- 

 mens produced under the best conditions. The starting point of M. Klein was the 

 steeling of engraved copper-plates, which process was effected in a bath composed of 

 the chlorates of ammonia and iron, to which ho added a small proportion of glycerine, 



