1853.] 



ON ELEOTROTYPING OPERATIONS. 



queutly a lofs from enlargement. It is not, therefore, by merely 

 increasing the battery siuiace that the time for eieetrotyping can 

 be shorloueJ. 



Mr. Sinee, the distinguished writer on electro-metallurgy, by 

 c:vering the negative plate of the battery with pulveruleut pla- 

 tinum, produced a veiy energetic form of the instrument. When 

 the plaie is freshly iilatmized, it acts violent!}-, and tljrows oft" 

 the hydi'ogvn in torrent=. But tins increased energy of the plate 

 is n'va lually lost, from the electric current depositing upon it 

 impurities from the zinc. 



As this deposit has a strong attraction for the hydrogen, it is 

 rettnncd on the plate. The ]jlate, being thus encased m air, is 

 virtually excluded from the liquid of the battei'y. Tlie ordinary 

 sob'ents of the metals do not i-eadily remove this coating of im- 

 purity. The plate can be renewed by replatinizatinn ; but, as 

 this is both tedious and expen-ive, I was urged to find a men- 

 struum which would restore ihe original platinum to its energy. 

 This I attained, at length, by immersing the plate in a solution 

 of per-chlorid of iron, whicli almost immediately restores the 

 action of the plate. 



The plates are nov?- daily immersed in the chlorid of iron, by 

 which the tone of the battery is constantly maintained. 



By this last discovery, together with obtaining better solutions 

 for the decomposing cell, the time for making a casting was re- 

 duced ; but still the time requii-ed for making a plate was too 

 long when ordy one electrical equivalent was employed. 



The effective force of one battery may be added to another. 

 This is increasing E in the formuhi, and this will sometimes in- 

 crease Q. 



We unite the effective force of many batteries by joining their 



dissimilar ends in consecutive order. As the current in such an 



arrangement has to traverse eveiy battery in the chain, R will 



be multiplied as many times as we multiply E. The formula 



n E 

 then becomes Q= „ , When the value of r and R are 

 n H-|-v 



neaily equal, and we have batteries of definite construction to 

 work with, it becomes a matter of some importance to determme 

 whethei- we shall use the whole galvanic apparatus, as a single 

 electrical equivalent, by connectiug all the similar parts of all 

 the battey cells, or whether we shall convert it into a ba'tery of 

 two pairs, in consecutive order, by joining dissimilar ends. As 

 dividing the battery is doubling R, and to double the electrical 

 eqivalents is also to double R, we shaU increase R fourfold by the 



E 2 E 



double an-angement. Instead of Q— g , - we have C2=j-jj^ , ^. 



Taking R=r we have Q=-50 in the single arrangement, and 

 Q^-io in the double — showing that we may double the ex- 

 pense, and yet make the casting moi-e slowly than before. Con- 

 ditions as above are of frequent occurrence, and a knowledge oL 

 them without experimenting is of very great importance. 



For R=l r, with a single equivalent of batter}', Q 



o 

 0-0909. For two batteries in series Q = 



l+iO 

 = 0-166. The 



2+10 



use of two batteries in consecutive order, as thus exhibited, 

 doubles the expense, but does not double the effect. A i-egard 

 for economy prohibits us fiom further increasing the series. To 



E / E \ 2 F. 



represent an effect double of =-i— '^ve have 2 ( -— ;— l=.r ; — 



R-fr \1-+'V ~ I' + r 



2 

 As di\-idin£r R by 2 is douliling the battery surface, we may now 

 make Q=-183. The gain per cent., now indicated by doubling 



the surface, makes it advantageous to make this increase when 

 two eonsecuti\e batteries are used. 



The difficulty of obtaining large flat plates of silver proved a 

 serious obstacle in effecting an inci-ease of battery surface, for the 

 ii'regukrity of the surface requires the plate to be placed at an 

 increased distance from the zinc, thereby augmenting R, the very 

 thing sought to be diminished. 



Plates could be made flat by the planishing hammer ; but the 

 operation being expensive, and the jilates continually liable to 

 accidents in use, economy ])r<iliibited this mode of forming flat 

 plates. Though the plating of metallic bodies with siher had 

 been well executed, it had not yet been determined that electro- 

 casting of silver could be executed in a desirable manner, and at 

 a modeiate expense and trouble At fii-st, every attempt to make 

 plates weighii'ig 2,500 grains to the square foot failed, on account 

 ot the inqjossibility of obser\ing Mr. Smee's laws of electro-metal- 

 lization for the time required. 



But after modifying the silutions of silver, and using a regis- 

 ter batter}', a plate could be made in thiity hours, perfectly flat, 

 and possessing the mechanical qualities of hardness, elasticity, 

 and malleability, in an eminent degree, and not costing over 16 

 cents per ounce for the making. 



The perfectly flat plates admit of a very close approximation 

 to the zincs. Their size may therefore be increased to more 

 than twice their former surface, as in the double arrangement, r 

 is relatively smaller to R 



Important changes have also been made in the modes of 

 operating, and in the arrangement of the apparatus. It had 

 early been noticed that changes of temperature influenced the 

 rate of working; and every electio-metallurgist knows the im- 

 portance of keeping the laboratory warm. 



To determine where and how the effect of temperature took 

 place, a battery, at 60 degrees Fahrenheit, was connected with a 

 wire 120 feet long, and enclosing a gahanometer. Tne deflec- 

 tion was 40 ° ; the battery was then cooled until the tempera- 

 ture was 48 ° ; the neeille was still deflected nearly 40 degrees. 



This experiment indicated that,the batteries were not greatly 

 affected by ordinary variations of temperature. Advantage was 

 then taken of this development to secure a more peifect ventila- 

 tion. Accordingly, a small room, to contain the battery, was 

 partitioned off fiom the general department by a glass pai-tition, 

 and laro;e outward openings made at the top and at the bottom 

 of the room, to gi\'e a circulation of air for carrying oft' the bat- 

 fumes. 



At the stage of improvement now described, one of our 

 medium plates, having eight square feet of surface, could be 

 readily made in from eight to ten days. But wishing still further 

 to quicken the process, or attain my fij-st desii-e — to deposit one 

 pound per day on the square foot, with a sinole equixalent of 

 battery — improvements were again sought after. As the E of 

 the formula has been increased to the gi-eatest extent the cost 

 would permit, and Rhad been diminished, or the ]ilates increased 

 in size to the greatest useful extent, it was sought to inci-ease Q 

 by diminishing r, or the electrolytic resistance. It was sought 

 to increjLse the conducting povver of the electrolyte by adding 

 easily decomposable salts to it; but with no success. The 

 accelerating effect of tempeiature being found, as above stated, to 

 be confined chiefly to the decomposition cell, it was evident that 

 by using the electrolyte alone, at a high temperature, a considerable 

 adsantage might ensue. 



To determine the most advantageous working temperature, 

 and the resulting gain of effect, a voltameter battery was connect- 



