Crystallization of Parisite. 543 



The analyses were made in duplicate and agreed closely. 

 Regarding the method of analysis it may be stated that the 

 earths were separated from lime by precipitation with ammonia 

 after the complete removal of fluorine by evaporations and 

 fuming with sulphuric acid in order to ensure that no fluorides 

 were precipitated with the earth-hydroxides. The cerium was 

 separated from the lanthanum and didymium by precipitation 

 of the cerium with chlorine in a potassium-hydroxide solution, 

 a departure from the method employed in the earlier analyses 

 of the Muso and Montana minerals. Care was taken to 

 examine all filtrates from oxalate precipitations of the earths to 

 recover, if present, any unprecipitated earths, a necessary pre- 

 caution, as has been pointed out by Hillebrand and others. 

 The results of these anahyses are given above and in parallel 

 columns are given for comparison the older analyses of pari- 

 site ; also the analyses of synchisite and cordylite. 



For synchisite the ratios derived from Flink's analyses are 

 sharply— C0 2 : F : E 2 3 : CaO=4 : 2 : 1 : 2. This leads to the 

 formula given by Flink, (EF) 2 Ca„(C0 3 ) 4 . The analysis of Mauze- 

 lius (7), though perhaps on less satisfactory material, leads to the 

 same formula. From this it appears that the formula of synchi- 

 site, as determined by Flink, differs from that of parisite in con- 

 taining exactly one more molecule of calcium carbonate. To 

 make the chemical compositions of parisite and synchisite iden- 

 tical calls for a change of 2*3 per cent in the C0 2 and of 6*0 

 per cent in the CaO. These are very serious differences, for 

 they involve unallowable errors in the determination of the 

 two constituents whose determination can be made with great 

 accuracy. Small differences in the proportions of the rare- 

 earth oxides are to be expected in minerals from different 

 localities, and, indeed, analytical errors in the determination of 

 the earths, unless considerable, would not seriously affect the 

 ratios on account of the large molecular weights of these 

 oxides. The close agreement in the lime and carbon dioxide 

 determinations of the Muso, Montana and Quincy parisites (in 

 all ten determinations have been made) leads us to place great 

 confidence in their correctness, as well as upon that of the 

 formula derived for the mineral from these localities. 



In discussing the analyses by Tschernik on the Manchurian 

 parisite we are at a disadvantage, as the discussion appears in 

 full only in Russian. The ratios derived from these analyses, 

 however, do not correspond, so far as we can see, with the 

 ratios given above for either parisite or synchisite, being far 

 more complex. The presence of considerable amounts of water 

 in all three analyses, as well as the variable and zonal character 

 of the crystals analyzed by Tschernik, suggests strongly that the 



