TANTALUM — BALKE 237 



The electrical resistance is quite high, about eight times that of 

 copper and about three time that of tungsten. The accompanying 

 table gives the physical properties of tantalum as far as they are 

 at present known, and also those of a number of other metals in com- 

 parison. 



HIGH CHEMICAL RESISTIVITY GIVES IT MANY USES 



In considering the possible uses for this metal we must take into 

 account its high melting point, its resistance to chemical corrosion, 

 and its tendency to absorb all of the common gases. We must also 

 remember that we are limited by its relatively low temperature of 

 oxidation. Tantalum seems to be a very desirable metal for the 

 manufacture of certain dental instruments and dental spatulas, and 

 undoubtedly for other dental and surgical tools or instruments. The 

 metal is not attacked by any of the antiseptics or chemicals used 

 and can be readily sterilized by heat. A surface film of hard ma- 

 terial about as hard as agate can be produced on the metal by proper 

 heat treatment. It will probably be found possible to harden the 

 material throughout, thus combining all the advantages of tem- 

 pered steel with absolute chemical inertness. 



It has been suggested for use in the manufacture of pens and 

 analytical weights. Its use in chemical laboratories and in the 

 chemical industries as containers, parts of pumps, and other equip- 

 ment will undoubtedly depend upon the cost at which the metal can 

 ultimately be produced. 



Tantalum is suitable for cathodes in electrochemical analysis. In 

 some respects it is more suitable than platinum. For instance, zinc 

 may be plated directly upon the tantalum, as it does not alloy with 

 the metal. Gold or platinum can be deposited upon the metal, as 

 they can be removed by aqua regia without attacking the electrode. 



Undoubtedly tantalum in the form of sheet, wire, or ribbon will 

 find application in the manufacture of radio sending and receiving 

 tubes. The property of tantalum of absorbing gases would seem 

 to make the metal its own " getter " in vacuum tubes, and would tend 

 to maintain the high vacuum required, particularly in the sending 

 tubes. It would seem that some part of the lamp made of tantalum 

 could be so constructed that at all times a portion of the metal 

 would be at the proper temperature to absorb gas and would, there- 

 fore, tend to maintain a vacuum equilibrium within the bulb. 



USE OF TANTALUM AS AN ELECTROLYTIC VALVE 



Tantalum has interesting possibilities on account of its property 

 of acting as an electrolytic valve. 



If two plates of bright tantalum metal are placed in an electro- 

 lyte and the two plates connected to an electric battery, there is an 



