332 
PHYSICS: E. L. NICHOLS 
TABLE I. 
T 
I 
i/vi 
U,UUU4/y 
0 1 ^0 
U . loU 
n AAA A 2 7 
Z / . / o 
0.000856 
16.02 
0.250 
0.000949 
12.62 
0.281 
0.00110 
9.80 
0.319 
0.00146 
5.03 
0.446 
0.00170 
2.03 
0.702 
0.00193 
0.971 
1.014 
0.00212 
0.610 
1.280 
0.00247 
0.296 
1.836 
0.00287 
0.159* 
2.524* 
* These values are probably 
somewhat less accurate than the 
other data given in this table. 
In Table I relative intensities /, the recipro- 
cals and times T after excitation are 
given. Figure 5 shows the relations between 
/ and r, and and T respectively in 
the usual manner. 
As appears from the table and curve ABC 
figure 5 this substance exhibits a remarkably 
rapid decay, falHng in the interval between 
0.0005 second after close of excitation and 
0.003 second to less than three-thousandths 
of its intensity at the beginning of that in- 
terval. To show the degree of accuracy with 
which the lower intensities were observed the 
portion of the curve {BC) is reproduced with 
ordinates magnified ten times {B'C). The 
results are likewise plotted in the customary manner with I/a// as 
ordinates (curve DEF) and this brings out an unusual characteristic 
hitherto unobserved so far as the writer is aware in studies of phos- 
phorescence except in the 
solitary case of parafiine re- 
corded by E. H. Kennard.^ 
It is usual to find two pro- 
cesses of phosphorescence 
succeeding one another and 
represented by the two 
straight arms of the curve 
DE and FG but in all the 
numerous cases hitherto de- 
scribed, excepting that of 
paraffine just noted where a 
very slight upward trend was 
found, the later process {FG) 
is indicated by a curve of les- 
ser slope. In the case of this 
uranyl salt, however, FG 
trends very sharply upward 
showing a greatly accelerated 
decay. Whether this peculi- 
arity is confined to these salts 
or is a common property of 
phosphorescence of exceed- 
A 
I 
-SO 
'■40 
b' ^' 
3- 
-SO 
V 
• / 
1 / *~ 
-20 
-10 
\ F 
D 
^C' 
^V^f !^ 1 
.001 SEC. 
.OOX SEC. .003 SEC 11 
FIG. 5. 
