570 HENRY A. ROWLAND 



The elements which persist to the last by the ferrocyanide process are 

 & and i, while by Kriiss' process the element d persists the longest. As 

 & -J- i has an absorption spectrum and d probably not, the test of purity 

 by absorption bands is very complete in the new process. 



Note. For help in this investigation my thanks are due to a large number of gen- 

 tlemen. Professor Schapleigh has sent me a large collection of substances, Mr. 

 Hidden, Professor Wolcott Gibbs, and Professor F. W. Clarke many minerals, Profes- 

 sor Kriiss several specimens, and Professor Barker and others have helped me in 

 many ways. 



