On Supersaturation of Salt-Solutions. 453 
I am sorry to say that I did not see this clearly at first, nor 
do I see it now as clearly as I should like, and I have accord- 
ingly wasted three days in an attempt to take account of 
conduction of heat, or at least of a certain minimum amount of 
it, as if it were an essential part of the process; the raising of 
heat-potential by the current in certain cases being only 
accountable, as it seemed to me, by reason of a definite and 
calculable amount of degradation by conduction ; after the 
manner of a water-ram. 
Liverpool, 8th May, 1885. 
LI. On Supersaturation of Salt-Solutions. By W. W. J. 
Nicot, M.A., D.Sc., Lecturer on Chenustry, Mason College, 
Birmingham”. 
“Te sulfate de soude dissous dans l’eau a des températures quelconques 
est anhydre. I] n’y a de solution sursaturée.’’t 
ieee I proceed to give an account of my experiments 
on this subject and the conclusions based on them, it is 
necessary to point out that there are two distinct kinds of 
supersaturation. 
Supersaturation, in general, may be defined as— 
The existence in solution of a larger quantity of salt than 
the water is normally capable of holding in solution at the 
temperature of experiment. 
Or as clearly expressed by Mulder {— 
“ Oververzadiging is: meer in oplossing hebben bij eene 
zekere temperatuur dan bij die temperatuur in oplossing kan 
overgaan, wanneer men begint met het vaste zout en dat 
behandelt met water bij die temperatuur. .. Oververzadiging 
is dus: behoud van een toesiand, aan het zout gegeven door 
eene hoogere temperatuur.”’ 
“ Supersaturation is the holding in solution at a given tem- 
perature more salt than can be dissolved at that temperature, 
starting with the solid salt and treating it with water at that 
temperature. Itis thus the possession of a condition which 
is conferred on a salt by a higher temperature.” 
Supersaturation as thus defined is common to all salts 
without exception. But it will be seen on reflection that, as 
I have said, there are two kinds :— . 
Ist. That occurring in presence of undissolved salt. 
* Communicated by the Author, having been read before the Royal 
Society of Edinburgh, April 1835. 
+ Loewel, Ann. d. Chim. et Phys. [3] xlix. p. 51. 
t Biydragen tot de Geschiedens, van het scheikundig gebonden Water 
(Rotterdam, 1864). 
