390 Prof. Connell on the American Mineral Nemalite. 



all that the acid used in dissolving the mineral, had left 

 undissolved. The rest of the ammoniacal precipitate con- 

 sisted of 0-16 peroxide of iron, and 0*29 of magnesia, which 

 were separated by benzoate of ammonia. The solution which 

 had been precipitated by ammonia was evaporated to dryness, 

 and ignited after excess of sulphuric acid had been added. 

 From the sulphate of magnesia thus obtained, solution in 

 water separated 001 more of silica. The sulphate weighed, 

 deducting the silica, 7*6 grains, equivalent to 2585 of mag- 

 nesia. In five grains of the mineral, there thus were, of solid 

 constituents, — 



Magnesia, 0-308 



2-585 

 2-893 



Protoxide of iron, 0*14:2 



Silica, 0-03 



0-01 

 0-04 



3-075 

 And in 100 parts, — 



Magnesia, , 57'86 



Protoxide of iron, . . , • , 2-84 



Silica, 0-80 



Water, ........ 27*96 



Carbonic acid, ...... 10*00 



99-46 



Considering the protoxide of iron as replacing a little mag- 

 nesia, it appears that the mineral is a combination of hydrate 

 of magnesia with a little hydrated carbonate of magnesia. 

 The formula, 5 MgO * HO + MgO • CO^ • HO, will nearly ex- 

 press its constitution, on that view, giving, 



3ia, 61*67 



Water, 27*24 



Carbonic acid, . . , , , , 11*09 



100-00 

 "We have an example of a mineral having an analogous 

 constitution, in the native hydrated carbonate of zinc (zink- 

 blUthe), for which M. Rammelsberg gi\%s the formula, 2 ZnO 

 •HO + ZnO-CO^-HO. 



