1909] on Tantalum and its Industrial Applications. 59B 



mercial scale, it has been possible to improve many details of the 

 process, so that the tantalum produced by it at the present time is 

 even purer than that shown in 1905 at the discourse of Dr. von 

 Bolton and Dr. Feuerlein. 



Some specimens of this latest tantalum have been submitted to 

 Sir James Dewar, who has very kindly made experiments with refer- 

 ence to its specific heat and to its thermal conductivity. 



He ascertained the specific heat by plunging small spheres of 

 tantalum, which had been heated to the temperature of boiling water, 

 into water of 14° C, then transferring them to melting carbonic acid 

 ( — 78' C.), and finally to liquid air ( — 188° C), and as an average 

 of several experiments the specific heat was found to be between 



100° C. and 14° C. = 0*033 



14° C. „ -78°C. = 0-032 



-78°C. „ -183°C. = 0-028 



while Dr. von Bolton in 1905 gave the specific heat as 0'0363. 



Multiplying these results by the atomic weight (181) it will be 

 seen that Dr. von Bolton's value (6*57) is slightly higher, and Sir 

 James Dewar's value (5*97) lower than 6*4, which, according to 

 Dulong and Pettit is the atomic specific heat. 



By the kindness of Sir James, his experiment for showing the 

 relative thermal conductivity of iron, copper and tantalum can be 

 repeated here by dropping three short rods, made of these metals, in 

 liquid air, while their tops, above the cardboard cover, are exposed 

 to the air of the room. 



In a short time the moisture of the air condenses on the rods and 

 freezes to a distance, which depends on the conductivity of each 

 metal. 



The results of Sir James Dewar's experiments prove tantalum 

 to have about three-quarters the conductivity of iron, and about one- 

 eighth the conductivity of copper. 



At ordinary temperatures, say below 300° C, pure tantalum resists 

 the action of all acids, except fluoric acid, of all alkalies, and of 

 moisture, so that it is an ideal material for chemical apparatus which 

 do not require high temperatures, and for any implements which, 

 when made of steel, are liable to rust. 



It has already been stated that pure tantalum is rough and malle- 

 able, so that it can be hammered out into thin sheets or drawn into 

 fine wire, the diameter of the filament wire being 0*03 mm. or 

 about one-eight-hundredth of an inch ; all the same, it is elastic and as 

 hard as soft steel, and has a tensile strength of 93 kg. per square mm., 

 which is equal to 57 tons per square inch. 



This means that the filament wire is capable of supporting about 

 80 grammes, or 2 - 8 ounces, as can be shown by actual experiment. 



Tantalum sheet can be stamped into various shapes, and out of 



