SKEY.— Oil as a Nucleus in Super-saturated Saline Solutions. 407 
Art. LXIII.—On the Mode in which Oil acts Mt a Nucleus in Super-saturated 
Saline Solutions ; with Notes on the Mode of Action of Solid Nuclei. By 
ILLIAM Sxey, Analyst to the Geological Survey Department. 
[Read before the Wellington Philosophical Society, 2ist February, 1880.] 
In a paper read before the Royal Society of England * On a relation 
between the Surface Tension of Liquids and the Super-saturation of Saline 
Solutions," by Charles Tomlinson and G. Van der Mensbrugghe,* it is 
stated that certain oils, both volatile and fixed, when applied to any of these 
solutions, “ act as powerful nuclei ;" that is, they cause the solidification of 
these solutions, by determining a crystallization of a portion of the salt 
thereof, which, when started even on the most minute scale, progresses 
sometimes slowly, sometimes at a speed giving an appearance of instanta- 
neous effect, until the whole of the solution has solidified ; a phenomenon 
which, I may remark, is of a somewhat striking character when witnessed 
and considered upon. 
This phenomenon is held by these investigators to be explained upon 
the theory, which they propound, “ that whatever tends greatly to lower 
the surface-tension of a super-saturated saline solution, causes a separation 
of salt, and at once puts an end to the condition of super-saturation." The 
theory is backed by formule, by frequent determination of tensions, and 
by experimental results of a very solid and varied character. But there 
are other results of theirs which do not appear in accordance with it, and 
the endeavours made to show them to be otherwise have the effect only 
of rendering this apparent unconformity the more conspicuous to me, and, 
besides that, of creating towards the theory itself a feeling unfavourable for 
its reception. 
It was under such an impression as to the insufficiency of the tension 
theory to account for all the facts given in their paper that, for a better 
understanding of the matter, I referred back to an investigation of mine, 
communicated to you last year; and by this I feel strongly persuaded that 
a factor in the problem—why oils sometimes act as nuclei ?—has been left 
out of it—and a factor of such high value, as to reduce the part which ten- 
sion plays therein (if, indeed, played at all) to one of a very subordinate 
character. This factor which I would bring to your notice is that of 
chemical affinity,—the affinity of one or more constituents of the oil used 
as the nucleus for the water of whatever solution is operated with. 
In the communication referred to “ On the Nature and Cause of Tom- 
linson’s Cohesion Figures," you may remember I stated the constitution 
of these figures to be fundamentally different from that which is assigned 
* Bee also London Chemical News, Vol. 25, p. 281. 
T Trans. N.Z. Inst., Vol. XI., p. 490. 
