M. Debray on some Crystallized Oxides. 57 



substance. Friedel proposes to give the name Wurtzite to this 

 dimorphous variety of zinc blende. 



Deville and Troost have also obtained this hexagonal blende 

 by a kind of sublimation. Some sulphuret of zinc placed in 

 trays in a porcelain tube, was heated to bright redness in a 

 current of hydrogen. No hydrogen was absorbed, and no trace 

 of sulphuretted hydrogen produced. Notwithstanding this the 

 sulphuret of zinc appeared as if volatilized, and was removed to 

 the cooler parts of the tube in the form of transparent crystals 

 of the greatest regularity. Hexagonal blende had been formed, 

 as was seen by a powerful action on polarized light. The re- 

 action had doubtless taken place in the following manner. The 

 sulphuret of zinc at a red heat had been reduced by hydrogen, 

 forming a mixture of zinc vapour and sulphuretted hydrogen. 

 Arrived slowly in the cooler parts of the tube, an inverse reaction 

 occurred; the zinc again took up sulphur to form hexagonal 

 blende, and hydrogen became free. It served as mineralizing 

 agent ; and the native sulphide may have been formed in the 

 same manner. That the volatilization of zinc was only apparent, 

 was proved by heating sulphide of zinc to a very high tempera- 

 ture in a current of sulphuretted hydrogen. No trace of subli- 

 mation was obtained in the porcelain tube. 



A number of crystallized oxides may be obtained by heating 

 in a platinum crucible a mixture of the sulphates of these 

 oxides and of alkaline sulphates. The oxide thus liberated at a 

 very high temperature in melted sulphate of potass or soda cry- 

 stallizes. Debray, who had previously obtained glucina in this 

 way, has also succeeded in preparing magnesia (periclase) and 

 oxide of nickel *. With sulphate of manganese pretty large cry- 

 stals of red oxide of manganese, Mn 3 4 , were obtained, but they 

 were so interlaced that it was impossible to measure their 

 angles with sufficient accuracy to be enabled to identify them 

 with Hausmannite. They have the same composition and hard- 

 ness ; the colour of their powder is the same, but the artificial 

 crystals are transparent. 



Alumina, magnetic oxide of iron, and green oxide of uranium 

 may be obtained by an analogous method, based on the decom- 

 position of certain phosphates by alkaline sulphates at a high 

 temperature. 



Gorup-Besanez f recommends the use of ozone for cleaning and 

 restoring the colour of old spotted and soiled books and prints. 



* Compies Rendus, May 13, 1861. 

 \ Liebig's Annalen, May 1861. 



