Intelligence and Miscellaneous Articles, 403 



acquires oxygen, appears to depend upon its physical properties ; for 

 when white lead is calcined in the same manner, the finest orange 

 minium is obtained by three operations, and it acquires 2*23 per cent, 

 of oxygen. 



M. Dumas observes that in no one of these cases has the massicot 

 in becoming minium combined with sufficient oxygen to convert it 

 into a sesqui-oxide, which it is well known the common red lead is 

 usually considered to be j for in that case it would give out 3'33 per 

 cent, oxygen instead of only 223 j when oxygen gas was passed over 

 it, 2*4 per cent, was the largest quantity of oxygen absorbed. This 

 minium M. Dumas found to consist of about 64*9 of protoxide and 

 35*1 of peroxide of lead, or two atoms of the former and one atom of 

 the latter j and this he considers to be the essential composition of 

 the miniums of commerce, mixed, as his experiments show, with 

 variable quantities of vellow oxide. — Ann. de Chim. et de Phys., torn, 

 xlix. p. 398. 



PREPARATION OF PEROXIDE OF HYDROGEN. BY M. THENARD. 



Those chemists who have prepared peroxide of hydrogen or oxy- 

 genated water, know that the peroxide of barium which they employ 

 always contains oxide of manganese - 3 that this oxide comes from the 

 porcelain retorts in which the nitrate of barytes is calcined, and that 

 it occasions the decomposition of a large quantity of oxygenated water, 

 at the moment of precipitating the solution. This decomposition in- 

 creases the difficulty of the preparation ; it is in fact the only real one. 

 I attempted to neutralize the effects of the oxide of manganese, and 

 accomplished it by the addition of a little phosphoric acid ; phosphate 

 of manganese is then formed, which does not act at all in decom- 

 posing the oxygenated water. 



Having then dissolved the peroxide of barium in the muriatic acid, 

 and obtained a liquor sufficiently charged with oxygen, 2, or at most 

 3 parts of concentrated phosphoric acid must be added for every 100 

 parts of oxide j the acid is to be supersaturated by hydrated and divided 

 peroxide, which will precipitate the silica and alumina, the iron and 

 oxide of manganese, the two latter in the state of phosphates. These 

 four substances become immediately deposited in the state of flocks, 

 and are to be collected on a cloth $ the liquor will readily pass through, 

 and may be filtered as wanted. 



In order that the operation may succeed well, it is requisite that 

 the saturation by means of peroxide of barium should be attempted 

 only with a tolerably clear solution. The presence of much sulphate of 

 barytes would be an obstacle to collecting the precipitate, and to the 

 filtration through linen. 



When the liquor is carried to such a point as to contain only water, 

 peroxide of hydrogen and muriate of barytes, sulphate of silver is to 

 be added in powder j this is to be very slightly acid, and may be obtained 

 by calcining pure nitrate of silver with sulphuric acid in a platina 

 crucible. The whole is to be stirred with a glass rod, and when the 

 muriate of barytes is quite or nearly decomposed, it will be known by 

 the liquor becoming clear ; then, in order to attain the point of perfect 



3 r 2 



JflSO isq '/inim oJni io-j 



loweasra ifoirfw >, fe smart** sill jfirfi g 



