schaller: identity of empressite with muthmannite 497 



increasing basicity. Its saturation curve is continuous with 

 that extending into acid sohitions. The solubility of the neutral 

 acetate in neutral solutions is 35.50 per cent. The extreme 

 basic solution in equilibrium with the neutral acetate contains 

 15.89 per cent PbO and 48.95 per cent Pb(C2H302)o. 



The tetra-lead-monoxy-hexa-acetate 3 Pb(C2H302)2.Pb0.3H20 

 crystallizes in needles which are usually minute, but may attain 

 the length of half a centimeter. It is exceedingly soluble in 

 water and forms solutions of density 1.93 to 2.28. The solu- 

 tions contain at the extremes of the satm'ation curve 15.89 per 

 cent PbO, 48.95 per cent Pb(C2H302)2 and 24.74 per cent PbO, 

 49.21 per cent Pb(C2H302)2. The substance is unstable in con- 

 tact with solutions of itself, but for its existence in equilibrium 

 with a solution it depends upon an excess of dissolved basic lead. 

 On account of the small size and softness of the crystals and the 

 high density of the mother liquor it is practically impossible to 

 isolate the pure substance. 



The tri-lead-dioxy-diacetate Pb(C2H302)2.2 PbO.4 HoO con- 

 sists of ill-formed needles which may be so small as to seem 

 amorphous. It is capable of existence in contact with solutions 

 of itself but under such conditions has a solubility of but 13.3 per 

 cent. Its saturation curve however possesses a very great length. 

 The extremes of solubility are 7.4 per cent PbO 4.8 per cent 

 Pb(CoH302)2 and 24.74 per cent PbO, 49.21 per cent Pb(C2H302)2. 



Lead hydroxide is stable in equihbrium with solutions contain- 

 ing as much as 7.4 per cent PbO and 4.8 per cent Pb (€211302)2. 



MINERALOGY. — The identity of empressite with mutlmmnnite. 

 ^YALDEMAR T. ScHALLER, Geological Survey. 



The name empressite has been given^ to a silver tellmide, 

 AgTe, from Colorado. A consideration of the data given does 

 not seem to justify its specific separation from the earlier described 

 muthmannite.- 



'Bradley, W. M., Empressite, a new silver-tellurium mineral from Colorado. 

 Amer. Jour. Sci. (4), 38: 163. 1914. 



^Zambonini, F., tJber den Muthmannit, ein neues Mineral, Zeitschr. Kryst. 

 Min., 49: 246. 1911. 



