EFFECT OF DRAWING ON THE DENSITY AND SPE- 
CIFIC RESISTANCE OF TUNGSTEN. 
WM. SCHRIEVER. 
It is known that the density of ductile tungsten wire changes 
when the wire is drawn to smaller diameters but the results of 
several experiments do not agree as to the nature of the varia- 
tion. Fink (Trans. Amer. Electro. Chem. Soc., 17, p. 229, 1910) 
gives data to show that the density increases with the drawing, 
the variation being 18.81 g/cm 3 before drawing to 20.19 g/cm 3 
when drawn to a diameter of 0.038 mm. His method of meas- 
urement was not described. Doctor Sieg, in working with a 
number of tungsten wires, also found an increase of density 
with the drawing. In a letter to Doctor Sieg, Doctor Worthing 
of the Nela Research Laboratory, National Lamp Works of the 
General Electric Company, gave Doctor Lorenz’s results on the 
variation of density with drawing. Doctor Lorenz used pyk- 
nometer and other ordinary specific gravity methods and found 
that the density decreases as tungsten is drawn finer and finer. 
His results are given in the following table : 
The following experiments were undertaken to determine 
whether the density increases or decreases as ductile tungsten is 
drawn to smaller diameters and also what effect this has on the 
specific resistance. 
It is known to those who have worked with tungsten that the 
physical properties vary if the heat-treatment is varied or if the 
mechanical working previous to drawing is varied. Since the 
material is heated during the process of drawing and since this 
heating cannot be maintained exactly the same we would expect 
the wires drawn at different times to have slightly different prop- 
erties. It is also impossible to swage two pieces of the metal 
in exactly the same manner previous to drawing and therefore 
wires made from different pieces of tungsten cannot be expected 
to behave in any regular manner. In order to eliminate, as far 
as possible, variations which might arise from these causes two 
Diameter of Wire. 
50 mils (swaged) 
20 mils (drawn) 
10 mils (drawn) 
5 mils (drawn) 
Density, g/cm 3 . 
19.1 
18.8 
18.5 
17.9 
