(1) The solubility of strontium sulphate in water
at temperature ranging from 25° to 100° has
been determined by a direct gravimetric method
and by a conductivity method. At 30° the
results obtained.. by the two methods agree
closely, the solubility at this temperature being
115 to 116 milligrams per litre.
According to the gravimetric method of determination, the solubility increases with rising
temperature, reaches a maximum at about 60°,
and falls again between 60° and 100°, whereas
according to the conductivity method the solubility decreases steadily with rising temperature, and at all temperature above 30° the
results are lower than those obtained by the
gravimetric method. The fact that the heat of
solution of strontium sulphate at ordinary
temperature is negative is in accordance with
the gravimetric results,(2) The solubility Of strontium sulphate in solutions
of sulphuric acid of varying concentration has
been determined. The "solubility effect" of
the common ion is less than would be predicted
by the "constant ionic solubility product rule",
but is greater than has been observed with more
soluble saturating salts.The solubility data were examined from the
point of view of the interionic attraction theory
as applied. by Noyes to the solubility effect of
one electrolyte on another. The experimental
results show only a very rough qualitative
agreement with the requirements of the theory
