668 



ARRHENIUS 



[chap. 25 



Table 



Distribution of Elements between Minerals Soluble in 1m Hydroxylamine 



Residue of 



a = below sensitivity limit. 



The reducible fraction contains the manganese oxide minerals. The acid-soluble fraction 

 consists mainly of goethite and, if present, the cations from hydrous aliuninosilicates (the 

 high iron content in the acid-soluble fraction of Dwd HD72 is partly caused by a non- 

 tronite with y}y— 1.598; Fe^+= 15%). Further, such apatite crystals in which substitution 

 with rare-earth ions is only partial are dissolved to a small extent in the weakly acid 

 hydroxylamine hydrochloride and extensively in the hydrochloric acid, which accounts 

 for the high concentration of rare earths, thorium, and possibly for the molybdenum and 

 lead found in the acid-soluble fraction. When considerable barito is present, as in AA 4711. 

 the corrosion of the crystallites yields appreciable amounts of barium, but the major 

 fraction of the mineral is left in the residue. 



