PROFESSOR W. C. ROBERTS-AUSTEN ON THE DIFFUSION OF METALS. 393 
Extract of four pages from the note book, showing method of calculating the 
results of two gold and two platinum diffusions in lead. The experiments 
were begun on October 9, 1894, and occupied 6'96 days. The mean tempera¬ 
ture was 492° C. 
Table A.—Tube 1. Gold in Lead. 
1 
Number 
of section 
of diffu¬ 
sion tube. 
2 
Weight in grammes 
of metal from each 
section— 
3 
Per¬ 
centage of 
gold in 
each 
section. 
4 
Corrected 
for 
density to 
equal 
volumes. 
5 
Divided 
b y 
0-005719. 
6 
Theoretical numbers 
for— 
7 
h 
2Vkt 
(by inter¬ 
polation) . 
lead-gold 
alloy. 
gold. 
h 0-11 
h n-m 
2 Vkt 01 ' 
2 y/kt ° ’ 
1 
263 
0T876 
713 
7-38 
1291 
1217 
1322 
0-117 
2 
3-20 
0-2247 
7-02 
7-26 
1270 
1188 
1286 
0-118 
3 
3T5 
0-2096 
6-65 
6-87 
1201 
1135 
1217 
0118 
4 
3-02 
0-1846 
6T1 
6-29 
1100 
1058 
1120 
0117 
5 
357 
0-1950 
5-46 
5-60 
979 
965 
1004 
0113 
6 
2-52 
0-1212 
4-81 
4-92 
860 
860 
874 
0110 
- 7 
316 
0-1317 
4-17 
4-25 
743 
749 
742 
0119 
8 
2-93 
0-1030 
3-52 
3-58 
626 
640 
613 
0-115 
9 
319 
0-0903 
2-83 
2-87 
502 
538 
496 . 
0119 
10 
2-67 
0-0593 
2-22 
2-24 
392 
447 
393 
0-120 
11 
2-74 
0-0477 
1-74 
1-75 
306 
370 
308 
0-120 
12 
2-61 
0-0354 
1-35 
1-36 
238 
310 
244 
0121 
13 
3T6 
0-0308 
0-97 
0-97 
170 
269 
201 
0-125 
14 
4-37 
00374 
0-85 
0-85 
149 
249 
180 
0125 
Sum. 
57-19 
Mean . 
0-1184 
h — 1’054 centims. when cold = 1"082 centims. at 492° C., therefore kt = 20'88. 
t = 6'96 days, therefore k — 3"00 sq. centims. per diem. 
The tables given by Stefan for calculating absolute diffusivities from the results of 
Graham's experiments with salts, give for special values of the factor the 
concentrations in each section of a diffusion cylinder, on the assumption that the 
original two volumes of diffusing solution of a salt, taken by Graham, contained 
10,000 units of salt. 
It follows from this that the sum of the numbers representing the concentration 
of the total number of sections will always equal 10,000. The numbers given in 
column 4 must therefore be divided by such a number as will make the sum of their 
quotients 10,000. This common divisor is found by adding up the numbers in 
column 4 and dividing the result by 10,000, and column 5 gives the quotients of the 
numbers in column 4 divided by the common divisor 0 005719. 
MDCCCXCVI.—A. 3 E 
