38 BARIUM, STRONTIUM, AND CALCIUM. 



sophical Transactions, vol. v., or to Silliman's Journal, vol. xxxii. p. 285, as 

 those which I employed were of the kind there described. There has, however, 

 been an improvement introduced. Formerly, the plates were secured by ce- 

 ment ; but, of late, I have had them so shaped and fitted as to slide out of the 

 grooves when pulled by means of forceps. This has enabled me to have them 

 washed after each operation, and, when necessary, scraped. 



Instead of a coating of cement, the wood is defended by mutton suet or bees' 

 wax, in which, while melted, it is soaked, after being made as hot as possible 

 without taking fire. 



I have found great benefit to arise from Mr. Sturgeon's expedient of amalga- 

 mating the surfaces of the zinc; which Faraday has represented as giving, 

 to a great extent, the properties of a sustaining battery. Agreeably to my 

 experience, it renders the plates less liable to be encrusted with suboxide of 

 zinc and copper, which always impairs the energy of a voltaic series. 



In order to facilitate the insertion or extrication of the plates into or out of 

 the grooves, the plates are cut so as to be about one-eighth in breadth less at 

 the lower ends. In addition to the advantage of being enabled to cleanse the 

 plates, this liberty of removing or replacing them is beneficial in another 

 respect. It must necessarily ensue, that those edges of the plates which are 

 lowermost, when the acid is in the act of being transferred, must be much 

 more corroded than those portions of the surface which are otherwise situated, 

 In fact, under the circumstances alluded to, the zinc is liable to be eaten 

 through, near one of the lateral edges, v,^hen otherwise not more than half 

 worn. But, in consequence of the construction above described, by a reversal 

 of their relative position, each edge may, in turn, be made lowermost, so as to 

 equalize the degree of corrosion sustained. 



Distillatory Apparatus and Process. 



A quantity of the amalgam, weighing about three thousand grains, was intro- 

 duced into an iron crucible. Of this crucible a section is 

 represented by Fig. 2, which was forthwith closed by a 

 capsule seated in a rabbet, or groove, made on purpose to 

 receive it. The capsule being supplied with about half 

 a dram of caoutchouchine, was then covered by the lid. 

 In the next place, by means of a moveable handle, or bail, 



