386 SIR WILLIAM CROOKES ON SCANDIUM. 



of which the purity and the history were known, rather than start afresh with acids 

 of unknown history. 



Many of the acids were prepared and purified by myself; for others I am under 

 obligations to friends, among whom I must specially thank Dr. O. SILBERRAD. 



I wish also to express warm thanks to Dr. VON MARTIUS for the munificent gift ot 

 100 gr. of almost pure scandia a gift which has enabled me to work on a larger 

 scale, and to preserve many specimens of analysed salts for future reference. 



