418 
MR. F. OSMOND AND PROFESSOR ROBERTS-AUSTEN 
area (striction) were determined, and the results given in the following table were 
published* in the Philosophical Transactions in 1888. 
Name of added 
element. 
Tensile strength. 
Elongation, 
per cent, (on 
3 inches. 
Impurity, per 
cent. 
Atomic 
volume of 
impurity. 
Reduction of 
area at fracture, 
per cent. 
Potassium 
Tons per sq. in. 
Less than O' 5 
Not perceptible 
Less than O'2 
45-1 
Nil. 
Bismuth . 
0'5 (about) 
0-210 
20-9 
9? 
Tellurium. 
3-88 
0T86 
20-5 
Lead .... 
4T7 
4'9 
0-240 
18-0 
Very slight. 
Thallium . 
6-21 
8-6 
0T93 
17-2 
15 
Tin. 
6-21 
12-3 
0196 
16-2 
Not measured. 
Antimony 
6'0 (about) 
qy- 
0-203 
17-9 
54 
Cadmium. 
6-88 
44-0 
0-202 
12-9 
See note f 
None. Pure gold 
7'00 
30'8 
none 
— 
Silver .... 
7-10 
33'3 
0-200 
10T 
Palladium 
7T0 
32'6 
0-205 
9-4 
75 
Zinc .... 
7-54 
28'4 
0"205 
9-1 
74 
Rhodium . 
7-76 
2.T0 
0’21 (about) 
8-4 
See note f 
Manganese . 
7'99 
29-7 
0207 
6-8 
60 
Indium 
7-99 
265 
0-290 
15-3 
72 
Copper 
8-22 
43-5 
0193 
7-0 
See note f 
Lithium . 
8-87 
21'0 
0-201 
11-8 
60 
Aluminium . 
8-87 
25'5 
0-186 
10-45 
46 
These results indicated, in a general way, that the tenacity and ductility of gold is 
increased by the presence of 0'2 per cent, of an added element of smaller atomic 
volume than that of gold itself, while on the other hand, these properties are 
diminished when the atomic volume of the added element is greater than that of 
gold. There are, as might be expected, exceptions and irregularities, but it is strange 
that they are not more numerous and more marked. The weight of the added 
element is in ail cases close to 0'2 per cent., but the atomic percentage differs widely. 
It will be interesting' to ascertain in a future research, what is the effect of adding to 
gold equal numbers of atoms of foreign elements. 
The investigations which have been conducted in later years have revealed the 
complexities of the question. Even the purest metals are not, from a mechanical 
point of view, homogeneous. Under the influence of internal forces which tend to 
make them crystalline, and of external stresses which are set up by contraction during 
cooling, the invisible molecules become arranged in visible and more or less highly 
organised groups. These groups are separated from each other either by planes of 
cleavage or by joints which are often surfaces of least cohesion, and therefore of 
weakness. This is especially the case when these joints have been accentuated by the 
evolution of dissolved gas at the moment of the solidification of the metal. 
In alloys, chemical homogeneity may, in turn, disappear, and free metals, chemical 
compounds, or various alloys, may fall out of solution from the liquid mass and finally 
* ‘ Roy. Soc. Phil. Trans.,’ vol. 179, 1888, A, p. 339. 
t These test-pieces drew out after the manner of pitch, that is, as a viscous solid. 
