TELLURIUM CRYSTALS' ' 
303 
NOTES ON THE PRODUCTION AND SOME ELECTRICAL 
PROPERTIES OF TELLURIUM CRYSTALS. 
W. E. TISDALE. 
This report deals with the production of Tellurium crystals, 
and the effect of temperature on their electrical properties. An 
investigation of Tellurium was undertaken primarily to settle 
the question of its change of resistance with light, or its light- 
sensitiveness. It occurs in the periodic table in the same column 
with Selenium, and in the same row with antimony, which ele- 
ments show an effect on light sensitiveness. Adams in 1876 made 
some experiments on Tellurium cells and reported ‘‘a distinct 
though very slight influence of light on their conductivity”. 
Siemens, Knox, and Saunders report that there is no effect of 
light that can not be explained as the effect of heat. Selenium 
crystals differ in certain ways from Selenium cells, and it was 
this fact that suggested the idea of securing Tellurium crystals 
for the tests. 
Tellurium is a non metal of atomic weight generally accepted 
at 127 ; it has its melting point at 452 C., and crystallizes in 
but one system, the hexagonal. Commercial Tellurium in stick 
form is sealed in a tube of heavy glass through which dry air 
and dry hydrogen gas have been passed a half hour in turn, 
and which 4s then placed in an electric oven where the tempera- 
ture is kept constant — the crystals forming by the process of 
sublimation. The lengths of the crystal axes seem to be a func- 
tion of the pressure under which they form. In an atmosphere 
of Hydrogen gas, under a pressure of three centimeters of mer- 
cury, the crystals form with nearly equal axes — from one to two 
millimeters. Under a pressure of three atmospheres in Hydro- 
gen, the length of the crystal is from twenty to thirty times its 
diameter, and the longest one produced here was 3.2 cms. long, 
requiring two weeks’ time to grow. The crystals form much 
more slowly in low pressure than in high — in the latter case 
they are evident in twenty-four hours, and have grown to more 
than one centimeter in three days. 
These crystals of Tellurium are exceedingly brittle, and it 
is not possible to solder them. If they are mounted for electri- 
