ELECTRO-METALLUBGY 219 



Those however, who have paid attention to this steeling process, have had occasion 

 ,to remark that in giving the deposit of iron a greater thickness, the surface cracked, 

 and the deposit detached itself from the cathode in excessively brittle flakes. It 

 became necessary, therefore, to employ baths of two different classes, composed of 

 sulphate of iron and sulphate or chlorate of ammonia. Finally, M. Klein devised 

 three baths, after the formula FeO, SO 3 + NH 4 0, SO 3 + 6HO. The first bath consists 

 of a concentrated solution of crystals of this double salt. The second bath was com- 

 posed by mixing the concentrated solution of each of these two salts in the propor- 

 tions of their equivalents. At length M. Klein obtained the third bath by taking a 

 solution of sulphate of iron, precipitating the iron by carbonate of ammonia, and 

 dissolving the precipitate by sulphuric acid, getting rid of all excess of acid. In pre- 

 paring the baths of the second class, M. Klein, as we have stated, mixed the solutions 

 of chlorate of ammonia and sulphate of iron in the proportions of their equivalents. 

 Another method employed is to dissolve in a solution of iron as much chlorate of am- 

 monia as it will readily absorb at a temperature of about 66 Fahr. All these baths 

 were concentrated as highly as they could be. As an anode, M. Klein employed iron 

 plates giving a surface about eight times that of the copper cathode. In using a 

 Daniell battery for the decomposition, the deposit was formed in twenty-four hours 

 upon the whole of the cathode. The deposit, however, was full of flaws, and was easily 

 detached and broken up into fragments. As it often happens that the solution of sul- 

 phate of copper improves by use, M. Klein hoped that the iron solutions would act in 

 a similar manner. He therefore continued the-experiments for several days, without, 

 however, obtaining any better results. Under the advice of Professor Jacobi, instead 

 of a pair of Daniell cells for each of the five stages of decomposition, he then employed 

 four pairs of feebler Meidinger cells, uniting them in series with the five stages of 

 decomposition. This arrangement was found to give a smaller development of hydro- 

 gen at the cathodes, and better final results. The deposits, however, were not yet 

 perfect, some exhibiting porosity, and others being furrowed. 



Conceiving from previous experience that this was due to acidification of the bath, 

 M. Klein tested it, and found a very decided acid reaction. He attributed this acidi- 

 fication to the circumstance that the quantity of iron deposited on the cathode was 

 greater than that dissolved by the anode. It was, therefore, necessary to give the 

 anode a greater degree of solubility, and as that could only be effected by increasing 

 its area, M. Klein conceived the idea of placing in the bath a plate of copper and 

 uniting it with the iron. The result of this combination was very remarkable ; not 

 only were the baths of the first class rendered neutral after several hours, but the 

 deposits became much more uniform. Their colour was a dull grey ; they adhered 

 perfectly to the cathode without warping or cracking in any part. During the first 

 24 hours the surfaces remained perfectly even ; but afterwards they began to exhibit 

 minute cavities similar to the appearances often produced upon galvanic deposits of 

 copper. These cavities, however, rarely penetrated to the depth of the deposit. 

 Their production is attributed to the superabundant disengagement of gas pn the 

 surface of the cathode. It probably happens that these bubbles attach themselves 

 strongly enough to hinder the formation of the deposit. If the energy of the current 

 becomes too great, these annoying phenomena are produced more frequently. By 

 reducing this energy in the process, and having only an imperceptible disengagement 

 of gas, by diminishing the concentration of the bath, or augmenting the resistance of 

 the solid portions of the circuit, the formation of these cavities entirely disappeared, 

 and the beautiful results to which we have already referred have been obtained. A 

 microscopical examination of the reverses of the deposits produced by M. Klein's 

 final process fails to discover any porosity or irregularity in the specimens. 



On leaving the bath the iron is as hard as tempered steel and very brittle. Ee- 

 heated to a dull red heat it loses much of its sharpness and hardness. Heated to a 

 cherry-red, it becomes malleable and may be engraved as easily as soft steel. If the 

 deposits are produced in good condition and annealed uniformly and with the ne- 

 cessary precautions, they are neither subject to warp nor bend. There is no contrac- 

 tion, but on the contrary, a slight degree of expansion, almost imperceptible however. 

 Owing to the necessity of having bank-note and similar plates identical in every 

 respect, it is of the first importance that they should not be distorted, nor have their 

 dimensions altered in the process of annealing. It appears that the galvanic deposit 

 of iron has not only permanent magnetism, but that, like soft iron, it receives the 

 magnetism of position. 



We have now reviewed both the failures and the successes of M. Klein. Of the 

 importance of the practical application of the process there can be no doubt whatever. 

 By replacing plates of copper by those of iron greater facilities will be afforded lor 

 producing publications, works of art, and especially bank-notes and cheques. Iron 

 electrotype plates are found to be almost indestructible. They not only can be 



