308 
IOWA ACADEMY OF SCIENCE 
Crystals of metallic selenium, S, figure 15, were placed in a 
metallic cup, C, attaclied to ttie vertical rod of a delicate elec- 
troscope, E. To melt the selenium a lens, L, for focussing the 
sun’s rays on the crystals, was employed; a flame would have 
been undesirable in this experiment because of itsi high ionizing 
power. With the rays shut off the electroscope was negatively 
charged. The focus of rays was then applied to the crystals, 
which soon began to melt, and in a short time fully 80% of the 
crystal mass had changed to the amorphous form. The time re- 
quired and the change of electroscope deflection were carefully 
noted. The cup was then cleared of the whole mass, the electro- 
scope again negatively charged, and the sun’s rays focussed as 
before, this time falling on the metal of the cup. The change 
in deflection was noted for the same time as previously required 
for the change of state. This was done also a second time. Thus 
there were two values for change in deflection to compare with 
the first result. If no important difference should appear be- 
tween these last two deflection changes and the change during 
the melting of the crystals, the conclusion would naturally fol- 
low that the change in state contributes of itself no appreciable 
charge to that already on the eleetroscope. 
NUMERICAL RESULTS. 
Total mass of crystals i.. 0.0142 grams. 
Mass of Se changing to amorphous form 0.01136 grams. 
Time consumed during change of state 3t^ mins. 
Readings of electroscope scale: 
At beginning of change of state 62 divs. 
At end of change of state 21 divs. 
Difference in deflections 41 divs. 
Readings of scale after removal of crystals from cup: 
First Trial. Second Trial. 
Beginning 
61 
Beginning 
.37 
End 
27 
End 
Difference 
34 
Difference 
39 
(Time during these trials, 31^ min., as in the first case.) 
The two trial readings indicate no important difference in 
change of deflection from that obtained during the change of 
state. Hence the conclusion tliat the state change has contributed 
no appreciable charge. 
