356 Dr.Wackenroder's Mineralogical and Chemical 



Consequently, 2*503 grammes of the diopside of Fassa are 

 composed of 



Silica (b) 1-3581 \ 



(c) 0*0020/ J Jb01gramme ' 



Lime (h) 0*6214 



Magnesia (i) 0*4577 



Protoxide of iron (d) 0*0629 



Oxide of manganese . . (f) 0*0025 \ ft . nai7 



(g) 0*0022 | uuu *' 



Alumina ,.(e) 0*0050 



•xygen. 



?7*07") 

 6*94 VU-i 

 7*28 J 

 0*54) 

 0*05 > 0*1 

 0*09 ) 



2*5118 grammes. 

 Accordingly, 100 parts of this diopside contain, 



Oxygen. 



Silica 54*154 27* 



Lime 24*740 6*94 



Magnesia 18*222 



Protoxide of iron .... 2*504 



Oxide of manganese .. 0*183 0*05 } 0*68 



Alumina 0*195 



100*001 

 If as the essential constituents of the diopside we take only 

 silica, lime and magnesia, the composition of this mineral 

 is to be expressed by two single bisilicates of lime and magnesia. 

 But this expression presupposes 2*74 per cent more silica than 

 the analysis has furnished; which difference, however, will be 

 reduced by one per cent, if we assume in the magnesia 38*71 

 per cent of oxygen ; consequently assume in the quantity of 

 magnesia found 7*05 parts of oxygen, instead of putting 20 as 

 its equivalent, as we have done in conformity with Gmelin's 

 latest Handbuch der Chemze, whose statement of equivalents 

 has been followed throughout in this calculation. 



If we wish yet to take into consideration, that, if the pro- 

 portion of magnesia should be diminished by so much as was 

 precipitated in the analysis («), but the omission of which may 

 have been assumed by chemists for the calculation of the cal- 

 cined magnesia, the magnesia first obtained would then con- 

 tain very nearly as much oxygen as the lime: we have ex- 

 actly such quantities of the principal constituents of the diop- 

 side, that the latter may be exactly expressed, in a chemical 

 point of view, by the symbols, 



(CaO + 2S*0) + (MgO + 2S* O) ; 



and in a mineralogical one by 



CS 2 +MS 2 . 



The 



