PEROXIDE OF TIN. (J03 



sesquisulphuret exists, corresponding with this oxide. The 

 salts of the deutoxide of tin have not been examined. 



Peroxide of tin, Stannic oxide, Sn O 2 , 935.3 or 74.92. This 

 constitutes the common ore of tin, which is generally crystal- 

 lized. The crystals of tin stone are sometimes brownish yellow 

 and translucent, at other times dark brown and almost black, 

 and contain small quantities of protoxides of iron and manga- 

 nese. Their primitive form is an obtuse octohedron of a 

 square base ; their density from 6.92 to 6.96. The peroxide of 

 tin in this state does not dissolve in acids, unless previously 

 ignited with an alkali. Tin is converted into a white powder, 

 which is a hydrated peroxide, by nitric acid ; and the acid acts 

 with most violence, when not of its highest degree of concen- 

 tration. This oxide, after being well washed and dried, contains 

 1 1 per cent of water ; it reddens litmus paper. After ignition 

 it assumes a pale yellow colour, and is equally insoluble, by the 

 humid way, as the natural oxide. 



To prepare the hydrated peroxide of tin, a solution of the 

 bichloride of tin should be precipitated cold, by an alkaline car- 

 bonate, and washed with cold water. It forms a white and 

 bulky gelatinous precipitate, which when collected on a filter has 

 a certain degree of transparency. In this condition the perox- 

 ide of tin is readily dissolved by hydrochloric acid, whether 

 concentrated or in a diluted state. Dried in vacuo at the usual 

 temperature, it forms hard translucent masses, resembling gum 

 Arabic, which contain not more than 1 eq. of water ; and is not 

 changed in properties by the desiccation. If this hydrated oxide 

 be digested in boiling water and collected again on a filter, it is 

 found, without much change in appearance, to be materially 

 altered in properties. The boiled oxide does not dissolve in 

 undiluted hydrochloric acid, but forms with a small portion of 

 it (about 14 per cent) a salt insoluble in an excess of acid. 

 When the excess of acid is decanted, the residue then dissolves in 

 pure water ; but it precipitates from the solution when hydro- 

 chloric acid is added. If the aqueous solution is boiled, the 

 oxide precipitates; and if the liquor is concentrated, it coa- 

 gulates like albumen. There can be little doubt that the pecu- 

 liarities of the boiled oxide are connected with an alteration in 

 its state of hydration. Peroxide of tin, prepared by the action 

 of nitric acid on tin, acquires the same properties, it is to be 

 presumed, from its being exposed to a high temperature in its 



