THE TANTALUM LAMP. 181 



any noticeable flame when ignited. It absorbs hydrogen as well as 

 nitrogen with great avidity, even at a low^ red heat, and forms with 

 them combinations of a metallic appearance, bnt rather brittle. It 

 combines with carbon very easily, forming several carbides which, 

 as far as they are at present known, are all of metallic appearance, 

 l)ut also very hard and brittle. The prodnct which Moissan thought 

 to be tantalum was clearly a carbide of this nature or an alloy of a 

 carbide with pure tantalum, for Moissan himself stated that his metal 

 still contained one-half per cent of carbon. Considering the high 

 atomic weight of tantalum (183) it is obvious that a very small quan- 

 tity of carbon suffices to carburize a relatively large quantity of 

 tantalum. This view of the constitution of Moissan's i)roduct is 

 confirmed by the properties he ascribed to the metal — namely, spe- 

 cific gravity 12 -8, great hardness and brittleness. These are not 

 properties of pure tantalum. When in the form of pow^der, still 

 containing, as previously stated, oxide and hydrogen, the specific 

 gravity of my material is about l-t; when purified by fusion and 

 drawn into wire it has a specific gravity of 16*8. It is somewhat 

 darker than, platinum, and has a hardness about equal to that of 

 mild steel, l)ut shows greater tensile strength than steel does. It is 

 malleable, although the effect of hammering is relatively small, so 

 that the oi^eration must be rather long and severe to beat the metal 

 into a sheet. It can be rolled, as well as drawn, into very fine wire. 

 Its tensile strength as a ware is remarkably high, and amounts to 95 

 kilograms per square millimeter, while the corresponding figure for 

 good steel is 70 to 80 kilograms, according to Kohlrausch, 



The electrical resistance of the material at indoor temperature is 



-105 ohm for a length of 1 meter and a section of 1 square milli- 

 meter (specific conductivity as compared with mercury 6*06). The 

 lenq^erature coefficient is positive and has a value of 0"30 betw^een 

 0° C. and 100° C. At the temperature assumed by the incandescent 

 filament in the lamp at 1 -5 watts per candlepower, the resistance 



1 ises to -830 ohm for a length of 1 meter and a section of 1 square 

 millimeter. The coefficient of linear thermal expansion between 

 0° C. and G0° C is 0-0000079, according to experiments made by the 

 Imperial Normal-Aichungs commission. Fusion is preceded by a 

 gradual softening, which appears to extend over a range of tempera- 

 ture of several hundred degrees. The specific heat is -0305, so that 

 the atomic heat is 6 '64, which is in accord with the law established 

 by Dulong and Petit. 



Part II. — By Dr. O. Feueklein. 



The results of the work carried out in our chemical laboratory, as 

 described by Doctor von P)olton in the first i)art of this j^aper, were, 

 of course, of the utmost interest to our incandescent lamp manufac- 



