No. V.] APPENDIX. 171 



silver wire will begin to dissolve ; in all other respects it is a delightful 

 instrument when you do not care about obtaining the maximum of power, 

 and you can obtain the galvanic principle by this means at a lower cost 

 than by any other way. The odds-and-ends battery is admirably adapted 

 for gilding and plating, or it may be employed for any operation that 

 requires much time for its performance. The charge for this battery 

 might contain one-third by measure of strong sulphuric acid, as the local 

 action is very trifling ; but it is found more advisable not to employ the 

 solution so strong, as, when nearly exhausted, the sulphate of zinc will 

 sometimes envelope the zinc and mercury, and prevent further action 

 before the top part of the liquid is fully saturated. An advantage of this 

 instrument is, that spelter, or raw zinc, may be used instead of manu- 

 factured zinc, and that no mercury is wasted, as the whole is left after the 

 solution of the zinc. 



" When we desire to employ a battery for manufacturing purposes, it 

 might be as well in some cases to remove the sulphate of zinc as soon as 

 formed, by means of a syphon tube passing to the bottom of the vessel, 

 while fresh acid is continually supplied at the top ; but this is not generally 

 necessary. For these purposes the battery should be so constructed, that 

 any of the zinc plates, when worn out, can be readily replaced. There are 

 many other forms which may be adopted, as the circular with the zinc 

 outside ; or it may be used as a tumbler battery. 



" The characteristic of this battery is the great quantity of electricity 

 produced, and its simplicity ; moreover, it requires but very little trouble 

 in its manipulation. The zinc seldom demands but one amalgamation, as 

 that will generally last till the metal is all dissolved. It is very important 

 to use for batteries zinc as pure as possible, for by that means the chance 

 of local action is materially lessened. The manufacturers of zinc plates 

 have a trick which is very fatal to this metal, for they buy up the refuse 

 or waste pieces which frequently contain solder, a composition of lead and 

 tin, and melt them with the raw zinc. This mixture always tells its tale 

 during the action of the battery, as a light spongy flocculent precipitate 

 rises to the top of the liquid, which is metallic tin, and when any particle 

 touches the zinc a little local battery is formed, which causes great waste 

 of metal. 



" In using this battery it is important that no salt of copper, lead, or 

 other base metal be dropped into the exciting fluid, as by that means the 

 silver would become coated therewith ; the plain consequence being, that 

 a surface of copper, instead of that of the finely- divided platinum, is 

 presented to the fluid. From a want of knowledge of this fact, in some 

 who have used the battery, I have seen the negative metal covered with 

 copper, which, finally becoming oxidated, rendered the platinum useless. 

 When this takes place, it is best removed by immersing the plate in dilute 

 sulphuric acid, to which a few drops of iiitro -muriate of platinum should 

 be previously added ; by this process the baser metals are dissolved and 

 metallic platinum thrown down. Some manufacturers prefer dipping 

 the silver into a solution of this sort every week. In this battery the 

 zinc is never reduced upon the negative metal, from the sulphate of 

 zinc formed during the action of the battery, so long as the exciting 

 fluid contains any acid at all. Other interesting matter connected with 

 this subject will be detailed when treating of the reduction of zinc." 



