196 ANNUAL OF SCIENTIFIC DISCOVERT. 



])l:itos or sheets does not obliterate tlieso eclls, but merely modi- 

 fies th(Mii, US they widen out under the pressure; the thin jiarti- 

 tions become laminated, and on the regularity of this lamination 

 the quality of the plate vi'ry much ilcpcnds. The cell system of 

 coi)per is more perfect than that of iron, a result of the pouring 

 of tlie copper into moulds, but the cells an; afterwards altered by 

 the pressure in rolling, etc., but never destroyed. If it were pos- 

 sible to make a section one-millionth part of an inch in thickness 

 these cells would be seen." — Drugjists'' Circular. 



BEHAVIOR OF METALS IN THE ELECTRIC CURRENT. 



If an electric current from a couple of cells of a Bunsen bat- 

 tery, the positive pole of which consists of a silver plate, is made 

 to pass through water acidulated with sulphuric acid, tiie silver 

 becomes covered with a black coating of amorphous peroxide of 

 silver. The formation of this oxide is due to ozone ; for, on sub- 

 stituting a jjlatinum plate for the one of silver, the smell of ozone 

 may be at once recognized. The same phenomenon takes place 

 if, instead of acidulated water, a solution of sulphate of sodium be 

 used. No peroxide is formed in a solution of nitrate of potassium, 

 but a flocculent, light-brown precipitate of oxide of silver forms 

 in the liquid. In a solution of fcrrocyanide of potassium the 

 silver becomes covered with a white film of fcrrocyanide of 

 silver (amorphous), and in a solution of bichromate of potassium 

 with a reddish-black lilm of crvstallized chromate of silver. 



When a plate of palladium is used as the positive electrode 

 in water acidulated with sulphuric acid, it becomes covered with 

 an almost black film of peroxide. Upon lead a coating of brown 

 peroxide, and upon thallium one of black oxide, is deposited. 

 Osmium, in its ordinary porous condition, is freely converted into 

 osmic acid. If, as an electrolyte, a dilute solution of hydrate of 

 sodium is employed, the solution assumes a deep-yellow color, 

 while at the same time metal is deposited on the negative elec- 

 trode. The same is the case with ruthenium. Osm-iiidium, in 

 its natural state, readily dissolves in the alkaline electrolyte. 

 — Wohler, Gotting. Nach. 



PURE IRON. 



Matthiesen prepares pure iron by the following method : Pure 

 dried ferrous sulphate and pure dried sulphate of sodium are 

 mixed in nearly equal proportions, and introduced gradually into 

 a red-hot j>latinum crucible. The mass is kept in fusion until the 

 evolution of sulj)hurous-afid gas ceases, then allowed to cool and 

 extracted with water. If the heat be jiropcrly regulated, the 

 whole of the iron is left as a verv line crvstalline oxide. This 

 oxide is thoroughly washed by decantation, to remove every trace 

 of the sulphate of sodium, and, after Ijeing dried, is reduced by 

 hydrogen in a platinum crucible; the spongy iron thus obtained 



