IN THE CURE OF THE STONE. ^9S
»,
much Mrs Stephens’s medicines mufl have fufFered in this way.'
For, as the air, in rendering the foap effete, ads only upon its ex¬
ternal furface, the more the furface is increafed, the greater will the
quantity be that is deprived of its virtue. Thus, fuppofe a cubical
piece of foap of four inches, made into twelve or fifteen hundred
pills, its furface, which was before only ninety-fix, will now, per¬
haps, be near a thoufand fquare inches; and confequently, in a
given time, the pills mufl lofe ten times more of their virtue, than
fuch a piece of foap, if allowed to remain whole. Soap fee ms alfo
to be rendered a good deal the worfe when reduced to a powder ;
whereby, not only its lithontriptic power is weakened, by its fur¬
face being thus increafed, and expofed to the air, but the watery
and oily parts of the foap being moftly evaporated, leave the alcaline
fait deprived in a great meafure of that which was intended to cor¬
rect it.
75. Dr Hales having been lately informed, that oifler-fhell
lime-water, mixed with fpir. nitri didcis, in the proportion of an
Englifh pint of the former to half an ounce of the latter, was a
more powerful folvent of the done out of the body than the lime-
water alone; in order to know the truth in this matter, he added
half an ounce of dulcified fpirit of nitre to a pint of oifter-ihell lime-
water, made by pouring a gallon of water on a pound of calcined
fhells, and having filled a phial of two ounces with this mixture, he
put into it a piece of a large calculus X, weighing twelve grains.
At the fame time he put into a like phial, filled with the lime-water
unmixed, another piece of the fame calculus Z, weighing eleven grains.
Both thefe phials were placed in a heap of dung, whofe warmth was
ninety-four degrees, according to Farenheit’s thermometer.
After forty-three hours, the furfaces of both thefe flones were
covered with a white mucilage ; but there was much lefs of this on
the calculus X than on Z1 the fame diiferen.ee was observed after
fixty-three hours; but after this it became lefs fenfible. In a few
nays after the phials were taken out of tue dung, the lime-water un¬
mixed loft its diffolving power entirely; but that to which the dul-
D d d 2 cified