VOLTAIC ELECTRICITY. 



fall particulars as to the beat mode* of proceeding, and tho 

 causes and remedies of the failures he may meet with. In 

 U'ssons we can only indicate the principles and general 

 otitlnu) of the art. 



The single-coll system is the simplest, and for ordinary pur- 

 poses will answer w.-ll. Tho whole may then bo arranged as 

 bhown in Fig. 02. A porous cell, A, of unglazed earthenware, 

 similar to those employed in 

 i iuiii'H's battery, must be pro- 

 i-ur.'.l, :in I liilr 1 with a weak 

 solution of Bnlphnrio acid (one 

 part of acid to from twelve to 

 twenty parts of water) or of 

 ln-iiie. A zinc rod or plate, B, 

 is immersed in this, and sus- 

 pended by a plug driven 

 through a hole in it, so that it 

 may not touch tho sides of the 

 cell. This is then placed in a 

 vessel, , filled with a saturated 

 * jlution of sulphate of copper, 

 to which a little sulphuric acid 

 has been added. As this solu- 

 tion would decrease in strength 

 by use, a small bag, E, of muslin or calico, filled with crystals of 

 the salt, is suspended in the vessel, and serves to maintain tho 

 strength. The wax cast of the medal having been well covered 

 with black lead, is now immersed in this solution, care being 

 taken to guard against air-bubbles remaining on its surface ; 

 the wire connected to it is then fastened to the binding-screw on 

 the top of the zinc rod. All is now 

 complete, and if the arrangements 

 have been properly carried out, a 

 deposit of copper will shortly bo 

 formed on the wire, and then will 

 spread gradually over the face of 

 the wax. The length of time re- 

 quired to form a deposit sufficiently 

 thick to bo removed with safety 

 depends upon the strength of tho 

 exciting solution. It is usually 

 found, however, that about twenty- 

 four cr thirty hours is sufficient. It 



is better to employ a somewhat weak exciting liquid, as many 

 moro failures are caused by tho power of the battery being too 

 great than by its being too small. When the current is powerful 

 tho metal is deposited moro rapidly, but it has a much coarser 

 grain, and is as a result much more brittle and uneven in texture. 



Sometimes the inner cell is dispensed with, and a partition 

 of porous wood or earthenware 

 is made across the cell (Fig. 

 C3), so that tho acid with the 

 zinc plate in it may be in one 

 compartment, and the copper 

 solution in the other. 



Though very good results 

 may be obtained in this way, 

 it is considered preferable to 

 employ a battery and decom- 

 posing coll separate from one 

 another. If an ordinary bat- 

 tery is employed, it should, 

 however, be as constant as 

 possible, and bo charged with 

 a weak exciting liquid. The 

 object to be copied is then 

 placed i:i the decomposing 

 cell and connected with the 



negative pole, while at a little distance from it there is suspended 

 a sheet of copper connected with the positive pole. Fig. 64 

 will illustrate the arrangcinent, Q being the battery, and tho 

 square vessel the decomposing trough. Two metallic rods, B 

 and r>, are laid across this, and connected respectively with the 

 two poles of the battery. From one of these the sheet of 

 copper is suspended, while from tho other hang the moulds 

 on which the copper is to be precipitated : care must be taken 

 that this one is connected with the zinc of the battery. Several 

 moulds may bo acted on at tho same time as shown. 



Fig. 64. 



From what has already been said, it will be at 

 -t...,.| that the solution of sulphate of copper will be decomposed, 

 and its copper thrown down on the negative pole, while a similar 

 amount of copper will be dissolved at the positive electrode. 

 Thus the copper plate, c, will IOM as much in weight an the 

 ni..iil-1-i will gain. The addition of crystals of the sulphate i 

 therefore, in this case, entirely unnecessary. 



When thin plan is adopted 

 it U well to allow rather more 

 time than with the tingle cell, 



aa then a more pliable deposit 

 is obtained. The temperature, 

 has, however, a considerable 

 effect in altering the speed of 

 the process, the action being 

 much mere rapid when the 

 temperature of the solution is 

 high, while in cold weather 

 scarcely any deposit can be 

 obtained without wanning it. 



There is one disadvantage in 

 the use of a vertical trough, and 

 that is that the solution be- 

 comes rather stronger at the 

 lower part, and consequently the deposit of copper is thicker at 

 the lower side of the mould than at the upper. With a small 

 mould the difference is too slight to be of much practical im- 

 portance, but with a large one it would cause inconvenience, and 

 seriously interfere with the result. To obviate this, the cell is 

 so constructed that the copper plate may lie flat on the bottom, 

 and the mould is then suspended 

 face downwards over it ; and in this 

 way a uniform thickness is attained. 

 When several moulds have to be 

 operated upon, a great saving may 

 be effected by using a trough divided 

 by means of partitions into a num- 

 ber of separate cells, as shown in 

 Fig. 65. Tho cells, a, b, c, d, e, are 

 virtually so many distinct cells ; 

 separate vessels may indeed be 

 employed if more convenient. At 

 the ends of the trough binding- 

 screws, N and p, are placed ; to one of these is fixed one ef 

 the moulds, A; to the other a plate of copper, B. The different 

 moulds are now taken, wires are fixed to them in the usual 

 way, and to the other ends of these wires plates of copper are 

 attached. Each wire is then bent so that the copper may be in 

 one cell and the mould in the next ; and the whole is arranged 



so that the moulds may all 

 face towards the positive pole, 

 as shown in the figure. 



The negative battery wire 

 may now be connected with N, 

 and the positive should be 

 placed against the copper 

 plate in cell a, until a deposit 

 begins to form on the mouH 

 in that cell ; then it may be 

 moved to the plate in 6, and 

 so on till it reaches the last 

 plate, B, when it may be 

 fastened to the screw, p. This 

 will render the action more 

 regular and certain in all the 

 cells. 



The great advantage attend- 

 ing the use of this compound 



trough is that for every equivalent of zinc consumed in the bat- 

 tery, an equivalent of copper will be deposited in each cell, and 

 thus if there are five cells, only about one-fifth the amount of 

 zinc will be dissolved that would be required if the other plan 

 were adopted. In the application of the art to business this i& 

 a matter of great importance. 



One of the most interesting, if not important applications of 

 electrotyping is to the art of pictorial illustration. Although 

 the pictures and diagrams in the POPULAR EDUCATOR and 

 other publications are rightly described as woodcuts in that 



66. 



