260 PROCEEDINGS OF THE A3IERICAN ACADEMY 



XYIII. 



NOTES ON THE OXIDES CONTAINED IN CERITE, 

 SAMARSKITE, GADOLINITE, AND FERGUSONITE. 



By Wolcott Gibbs, M. D., 



Rumford Professor {Emeritus) in Harvard University. 



Presented June 14, 1893. 



In the present paper I have brought forward a number of observa- 

 tions and analyses which I hope will be of service to those who are 

 engaged in the study of the rarer earths. The subject is one of such 

 extreme ditficulty, that even the results of an imperfect study may 

 have value. 



For the material which I have employed I have been chiefly indebted 

 to Dr. Waldron Shapleigh, Chemist to the Welsbach Incandescent 

 Light Company, by whom I have been liberally supplied with various 

 preparations in a state of considerable purity. I have also to make my 

 acknowledgments to Professor Everhart, fi'om whom I have received 

 a considerable quantity of gadolinite from the well known locality in 

 Llano County, Texas. The material given me by Dr. Shapleigh con- 

 sisted in part of beautiful crystalline double nitrates of the earths and 

 ammonium, and in part of crude oxides. The double nitrates contained 

 only the earths present in cerite, and for the most part only CegOs, 

 LugOa, PS2O3, and NdoOs, with very small relative quantities of Y0O3, 

 and traces only of other earths. In converting the crude oxides into 

 sulphates it is best to sift the fine powder slowly upon the surface of 

 cold dilute sulphuric acid. The sulphates are then formed at once 

 as fine crystalline powders free from hard lumps. Another method 

 sometimes applicable with advantage consists in mixing the oxides 

 with an excess of ammonic sulphate, and then igniting slowly in por- 

 celain crucibles, which are to be heated in a muffle to low redness until 

 vapors are no longer given off". The sulphates then present a beautiful 

 snow-white soft crystalline powder, and readily form saturated solutions 

 with cold water. In all work with the rare earths, oxalates from 

 their insolubility play a very important part. They may, as all chem- 

 ists know, be readily converted into sulphates by treatment with sul- 



