1888.] current on saturated solutions. 229 
experiments, and the amounts of salt dissolved during the cooling 
—considering the much shorter time in the electrical experiments 
and the more rapid fall in temperature—were not dissimilar. 
During the passage of the current however no alteration in the 
strength of the solution was detected, while in the case of pure 
heating, a very decided alteration took place. The conclusion 
can hardly be avoided that the current acted as a check on the 
process of solution. Considering however the great rise in tem- 
perature the very slow effect: of the heating, even when no current 
was present, seems very remarkable. 
That the current cannot wholly prevent the salt dissolving 
under all circumstances is obvious from the experiment on Dee. 9th, 
but the increase after the current stopped was still more decided. 
On this occasion the solution was certainly not saturated. 
The results of the experiments on potassium and calcium 
chlorides thus agree in representing the action of the current as 
most probably retarding the rate at which salt dissolves in a 
nearly saturated solution. They also emphasise the extreme slow- 
ness with which the salt naturally dissolves in such a solution. 
The following specific gravities of saturated solutions, all 
referring to temperatures very close to 15°, were taken with a 
common hydrometer. The solutions had all contained undissolved 
salt for not less than three months prior to the observations : 
Ammonium chloride 1:076. 
JPowaistsrten © Seansosor 1:169. 
OCU ME ete oeeiee 1:206. 
(Chilciomaw WS “ase5eece 1:394. 
(3) On compounds of arsenious oxide with sulphuric anhydride. 
By R. H. Apts, B.A., Trinity College. 
Arsenious oxide is readily soluble in sulphuric acid of various 
strengths when they are heated together. LExcess of the oxide 
first crystallizes out, and the mother liquor on agitation deposits 
crystals of fairly constant composition for each strength of acid. 
Crystals were obtained corresponding to 
AsO, . 480,, 
As,O, . 2S0,, 
ASOr SOs 
(OXON SOE 
