igoS.] NEODYMIUM AND PRASEODYMIUM. 'J97 



the case of some salts the spectra point to the existence of solvates 

 of varying complexity, in the case of salts of neodymium and 

 praseodymium they indicate rather the existence of one definite 

 hydrate. A more extended study, including the changes in the 

 spectra produced by changes in temperature, may, however, some- 

 what modify this conclusion. 



Granting the existence of solvates all of the facts observed in 

 connection with the absorption spectra of neodymium and praseody- 

 mium salts can be readily explained. 



Physical Chemical Laboratory, 

 Johns Hopkins University, 

 June, 1908. 



