692 
PROFESSOR ROSCOE’S RESEARCHES ON VANADIUM. 
the air, and as often boiled out with a solvent for vanadic acid, before they can be freed 
from the absorbed metal. If the platinum be frequently used for the reduction without 
this purification, it becomes brittle and dark-coloured from absorption of metal in 
quantity. 
My best thanks are due to Messrs. Oelhofek and Finkelstein, who have ably assisted 
me during the progress of the above investigation. 
