30 Proceedings of the Royal Physical Society. 
gentlemen, for the honour which you conferred upon me in 
electing me to the position of your President, a position 
which I now hand over to my successor. I wish also to take 
this opportunity of expressing my grateful sense of the 
friendly indulgence which I have received at your hands, 
and of the assistance which has been freely given to me by 
the officers of the Society during my term of office. 
I. Note on the Svlubility of Gypsum in Solutions of Sodium 
Chloride. By T. Curapert Day, F.C.S. 
(Read 19th December 1894.) 
It has been long known that water containing sodium 
chloride is capable of taking up a considerable quantity of 
gypsum (SO,Ca.20Hz2) into solution, probably owing to a 
certain amount of double decomposition taking place 
between the two salts. 
The question is one of considerable importance from a 
geological point of view, and a knowledge of the degree 
of action of solutions of sodium chloride of various strengths 
would aid our conception of the power of this agent in 
removing gypsum as it occurs in geological formations to 
which it has access. 
I have consulted the following authorities on the subject, 
but the information I have been able to obtain is rather 
meagre :— 
Thorpe’s “Applied Chemistry,” vol. i., states that “Gypsum 
is very slightly soluble in water, the solubility is increased 
by the presence of the chlorides of ammonium and sodium, 
hence its presence in salt springs.” 
Roscoe and Schorlemmer, vol. iti.: “1000 parts of 
water dissolve at 0° C. 2°05, at 35° C. 2°54, and at 100° C. 
less than 2 parts of gypsum. In presence of common 
salt gypsum is more readily soluble. According to Anton, 
1000 parts of a saturated solution of common salt dissolve 
8-2 parts of gypsum.” 
Watt’s “Dictionary of Chemistry,” vol. v., old edition: 
