[ 16G J 



XXXIV. On Cadmium. By William Heuapath, Esq. 

 To the Editors of the Philosophical Magazine and Journal. 



Bristol, 5G Old Market Street, August ]G, 1823. 

 T PUBLISHED a paper in the Annals of Philosophy for 

 -*■ June, 1822, on this new metal, in which I promised, that if 

 any thing pecuHar pi'esented itself in my examination, I would 

 commiuiicate it to the public, I did not then prosecute the 

 inquiry as much as I expected ; but my attention has been 

 drawn to this amoufr other metals latelj-, and I hasten to give 

 you some of the results ; as, notwithstanding their insignifi- 

 cance, they Avill tend to place the pure metal in the hands of 

 English chemists in greater quantity than it has hitherto been 

 procured. 



The process for obtaining jnn-e cadmiiun recommended by 

 Stromeyer is troublesome, and requires a considerable quantity 

 of carbonate of ammonia for the re-solution of zinc and copper, 

 besides which, if a little iron was contained in the substance, 

 it would be left with the cadmium ; as the sulphate of per- 

 oxide is precipitated by sulphuric hydrogen, dissolved by mu- 

 riatic acid, and is not redissolved by excess of carbonate of 

 ammonia. 



Tiiat ingenious chemist Dr. Wollaston has also projiosed a 

 mode which is faulty ; inasmuch as he directs iron to be placed 

 in the solution to precipitate any metals which have an mferior 

 affinity ; and then zinc to be used for the same purpose ; but 

 if iron throws down any thing, a corresponding portion of 

 itself must be dissolved, and this portion would be found with 

 the cadmium, whether in the state of carbonate or oxide. This 

 process would be rendered perfect by subliming the last pro- 

 duct in the way detailed below, which is the most simple 

 method I have yet found, and furnishes the purest metal. 



In the paper above mentioned I described a powder found in 

 the zinc works : if this be introduced into an ii'on bottle and 

 tube, (similar to that used Ibr obtaining oxygen gas from per- 

 oxide of manganese,) a piece of paper pushed down upon it, and 

 the apparatus placed above the neck in any furnace or fire-place, 

 where a brigh.t red heat can be produced, the cadmium will 

 be found in the cold part of the tube, or resting on the chaired 

 paper, if a larger quantity has sublimed than can support itself. 

 Phis is very nearly pure ; if not sufficiently so, the process 

 should be repeated. It now exists as small globules, adhering 

 ta tlie sides of the subliming vessel ; it may be reduced to a 

 button in the way recommended in the Annals of Philosophy, 

 June 1822, p. 4.36. 



It is necessary to have a small quantity of some substance, 



such 



