602 Ford and Bradley — Hetcerolite from Leadville. 



hydrogen sulphide gas. The precipitate was filtered upon an 

 asbestos mat in a filter tubef and ignited in a current of hydro- 

 gen sulphide. The filtrate from the zinc precipitate was 

 boiled to remove the hydrogen sulphide and then an excess of 

 bromine water and ammonium hydroxide was added. The 

 resulting manganese dioxide precipitate was filtered off, dis- 

 solved by hot sulphur dioxide water and the manganese repre- 

 cipitated by hydrogen sodium phosphate and finally weighed 

 as manganese pyrophosphate. The available oxygen was 

 determined by the oxalic acid method. 



The results of the analyses by Bradley follow. The partial 

 analysis by Haigh is also giveci in the last column. 



I II Average Ratios Anal, by Haigh 



ZnO 37-41 37-70 37*56 0-461 37'1 



MnO 50-29 50-39 50'34 0-709 45*9 



O 5-99 5-99 5-99 0:374 5-9 



CaO trace trace trace 



H 2 4-37 4-36 4*36 0-242 4'7 



SiO„ 2-69 2-70 2-69 0-044 Insol. 2'0 



100-75 101-14 100-94 

 Mn 2 3 55-95 56-06 56'00 0'354 



Ignoring for the present the small amount of silica shown 

 by the analysis, the molecular ratios have the following rela- 

 tions : The manganese protoxide is to the available oxygen as 

 0-709:0-374 or as 2-00:1*05. Evidently, the manganese is 

 present in the mineral as the sesquioxide, Mn 2 3 . This 

 assumption is borne out by the facts that although the manga- 

 nese is in the form of a higher oxide, since there is an excess 

 of oxygen present, it cannot be in the form of the dioxide 

 because when the mineral is heated in the closed tube there is 

 no oxygen liberated. The percentages of Mn 2 3 , calculated 

 from the amounts of MnO that were found, are given above. 

 On this assumption the ratios become ZnO : Mn 2 3 : H 2 0= 

 0-461 : 0*354 : 0*242 or as 1 : 0*76 : 0*52. These results might 

 be taken to indicate that the formula of the mineral was 

 4Zn0.3Mn 2 3 .2H 2 0. 



It seems, however, impossible to neglect the presence of 

 the silica. As this exists in a soluble form, it is probably pres- 

 ent as a definite mineral molecule. As the hetserolite is inti- 

 mately associated in its occurrence with calamine, it is 

 reasonable to suppose that the silica is present as a part of that 

 mineral. The physical structure of the material analyzed was 



* This Journal, xxi, 453, 1906. 



