502 



Professor W. Chandler Roberts- Austen [March 15, 



finely divided metallic aluminium. The thermo-junction (A, Fig. 1) 

 of the pyrometer which formed the subject of my last Friday Evening 

 lecture here, is placed within the crucible B, and the spot of light C, 

 from the galvanometer D, with which the junction is connected, 

 indicates on the screen that the temperature is rising. You will 

 observe that as soon as the point marked 1010° is reached, energetic 

 action takes place : the temperature suddenly rising above the 

 melting-point of platinum, melts the thermo-junction, and the spot of 

 light swings violently ; but if the crucible be broken open, you will 

 see that a mass of metallic chromium has been liberated. 



The use of alkaline metals in separating oxygen from other 

 metals is well known. I cannot enter into its history here, beyond 

 saying that if I were to do so, frequent references to the honoured 

 names of lierzeliue, Wohler and Winkler would be demanded.* 



Mr. Yautin has recently shown that granulated aluminium may 

 readily be prepared, and that it renders great service when employed 

 as a reducing agent. He has lent me many specimens of rarer metals 

 which have been reduced to the metallic state by the aid of this finely- 

 granulated aluminium ; and I am indebted to his assistant, Mr. Picard, 

 who was lately one of my own students at the Royal School of Mines, 

 for aid in the preparation of cerlain other specimens which have been 

 isolated in my laboratory at the Mint. 



The experiment you have just seen enables me to justify a 

 statement I made respecting the discriminating action which certain 

 metals appear to exert. The relation of aluminium to other metals 

 is very singular. When, for instance, a small quantity of aluminium 



* An interesting paper, by H. F. Keller, on the reduction of oxides of metals 

 bv other metals, will be found in the 'Journal of the American Chemical 

 Society,' December 1*'J4, p. S33 



