of Chondrodite, llumite and Clinohumite. 191 



These results, although low, are within - 15 and 10 per 

 cent of the theory when expressed in terms of the mixture of 

 chrysolite and fluorite. The iron was separated from magnesia 

 by ammonium, the precipitation being repeated at least twice 

 to ensure a complete separation. Water was sometimes 

 weighed directly in a U tube containing sulphuric acid, the 

 mineral being fused with anhydrous sodium carbonate in a 

 Gooch* tubulated crucible, special pains being taken to sur- 

 round the crucible in which the fusion was made by a larger 

 one containing sodium carbonate. Thus the gas flame never 

 came into direct contact with the inner crucible and the pas- 

 sage of gases through the red hot platinum, which would have 

 rendered the results too high was avoided. This method has 

 been carefully tested by us and gives accurate results. In 

 some analyses, where the percentage of ferrous oxide was 

 small, water was determined as loss on ignition, as follows : 

 .About 04 gram of lime was ignited to a constant weight in a 

 platinum crucible, into which subsequently the mineral was 

 weighed. The lime was then carefully slaked and mixed with 

 sufficient water to make a thin paste ; after drying down on 

 the water bath the crucible was ignited, gently at first, finally 

 over the blast lamp, to a constant weight. The lime keeps 

 fluorine from escaping and the error which would result from 

 the complete oxidation of the iron would amount only to a 

 few hundredths of one per cent. Duplicate determinations 

 made by both methods agreed very well with one another. 

 The water determined in the analyses must have come from 

 hydroxyl as it cannot be completely expelled from chondrodite 

 except by intense ignition. Thus a sample from Warwick, 

 ~N. Y., which by direct determination yielded 1*43 and 1*48 

 per cent, gave only 0*48 per cent when ignited in a glass tube 

 over the blast lamp, lime being used to retain the fluorine. 

 The method that has been usually adopted of igniting with 

 lead oxide was also tested and found to be wholly unsuitable, 

 two determinations yielding only 0'11 and 0*56 per cent. 



Chondrodite, {llumite Type II of Scacchi.) 



Chondrodite from Warwick, Orange Co., N. Y. — The 

 material that was selected for analysis was obtained from a 

 specimen in the Brush collection, Catalogue No. 2054. The 

 chondrodite occurs as rounded grains, of a rich reddish-brown 

 color imbedded in a white crystalline limestone and associated 

 with spinel and graphite. The material was very fresh and 

 showed occasional crystal faces, but not sufficient for the iden- 

 tification of the mineral. It was selected at the beginning of 



*Am. Chem. Jour., ii, p. 247, 1880. 



