358 REPORT—1905. 
The metals experimented with by Mr. Hadfield were all in the annealed or 
crystalline condition, so that the molecules must have exerted their mutual 
attractions along the directed axes proper to this state. It is to be expected that 
similar experiments with the metals in the amorphous state may throw light 
on the question whether and to what extent the crystalline state depends on a 
dynamic equilibrium between the forces of cohesion and repulsion, or whether 
a directed cohesion exists fully developed in the molecules at the absolute zero,! 
The phenomena of the solid state throw an interesting light on the interplay 
of the two great forces, the primitive or blind cohesion which holds undisputed 
sway at the absolute zero, and the repulsion due to the molecular vibrations which 
is developed by heat. This interplay we know continues through the states 
which succeed each other as the temperature is raised, till a point is reached 
at which the molecular repulsions so far outweigh the cohesive force that the 
substance behaves like a perfect gas. The problems of molecular constitution are 
more likely to be elucidated by a study of the successive states between the 
absolute zero and the vaporising temperature than at the upper ranges where 
the gaseous state alone prevails. The simplicity of the laws which govern the 
physical behaviour of a perfect gas is very attractive, but we must not forget 
that this simplicity is only possible because repulsion has so nearly overcome 
cohesion that the latter may be practically ignored. The attractiveness of this 
simplicity should not blind us to the fact that it is in the middle region, where 
the opposing forces are more nearly equal, that the most interesting and illumi- 
nating phenomena are likely to abound. ‘The application of the gas laws to the 
phenomena of solution and osmosis appears to be one of those cases in which 
an attractive appearance of simplicity in the apparent relations may prove very 
misleading. 
Before passing from the specially metallic qualities of gold I will only remind 
you of the important part it has played in the researches on the diffusion of 
metals by the late Sir William Roberts-Austen, and in those of Mr. Haycock and 
Mr. Neville on the freezing-points of solutions of gold in tin, which led to the 
recognition of the monatomic nature of the molecules of metals. 
Molecules in Solution. 
It has occurred to me that the practice of the cyanide process of gold extrac- 
tion presents us with several new and interesting aspects of the problems of 
solution. As you are aware, the gold is first obtained from the ore in the form 
of a very dilute solution of cyanide of gold and potassium from which the metal 
has to be separated, either by passing it through boxes filled with zine shavings, 
or by electrolysis in large cells 
The solution as it leaves the cyanide-vats may contain gold equal to 100 grains 
or more per ton, and as it leaves the precipitating-boxes it may contain as little 
as | or 2 grains and as much as 20 grains. In the treatment of slimes much 
larger volumes of solution have to be dealt with, and in this case solutions con- 
taining 18 grains per ton have been regularly passed through the precipitating- 
boxes, their gold content being reduced to 1} grain per ton. In round numbers 
we may say that 1 gram of gold is recovered from 1 cubic metre of solution, 
while 0:1 gram is left in the solution. Even from the point of view of the 
physical chemist we are here in presence of solutions of a very remarkable order 
of dilution. A solution containing 1 gram per cubic metre is in round numbers 
N/200,000, and the weaker solution containing 0:1 gram is N/2,000,000. It is 
convenient to remember that the latter contains a little more than 1} grain per 
ton. In experiments on the properties of dilute solutions the extreme point 
of dilution was reached by Kohlrausch, who employed solutions containing 
1 Since the above was written a series of observations has been made on the 
influence of low temperature on the tenacity of pure metals in the amorphous 
condition. These observations will form the subject of a separate communication 
to the Section. : beg : 
