Concretes expos'd to Calcination, to the salts obtain'd by it; I shall
rather, to shew the Disparity of salts, mention in the first Place the
apparent Difference betwixt the Vegetable fixt salts and the Animal
Volatile ones: As (for Example) betwixt salt of Tartar, and salt of
Harts-horn; whereof the former is so fixt that 'twill indure the brunt
of a violent Fire, and stand in fusion like a Metal; whereas the other
(besides that it has a differing tast and a very differing smell) is
so far from being fixt, that it will fly away in a gentle heat as
easily as Spirit of Wine it self. And to this I shall add, in the next
place, That even among the Volatile salts themselves, there is a
considerable Difference, as appears by the distinct Properties of (for
Instance) salt of Amber, salt of Urine, salt of Mans Skull, (so much
extoll'd against the falling Sicknesse) and divers others which cannot
escape an ordinary Observer. And this Diversity of Volatile salts I
have observ'd to be somtimes Discernable even to the Eye, in their
Figures. For the salt of Harts-horn I have observ'd to adhere to the
Receiver in the forme almost of a _Parallelipipedon_; and of the
Volatile salt of humane blood (long digested before distillation, with
spirit of Wine) I can shew you store of graines of that Figure which
_Geometricians_ call a _Rhombus_; though I dare not undertake that
the Figures of these or other Saline Crystals (if I may so call Them)
will be alwaies the same, whatever degree of Fire have been employ'd
to force them up, or how hastily soever they have been made to convene
in the spirits or liquors, in the lower part of which I have usually
observ'd them after a while to shoot. And although, as I lately told
You, I seldom found any Difference, as to Medical Vertues, in the fixt
Salts of Divers Vegetables; and accordingly I have suspected that most
of these volatile Salts, having so great a Resemblance in smell, in
tast, and fugitiveness, differ but little, if at all, in their
Medicinal properties: As indeed I have found them generally to agree
in divers of them (as in their being somewhat Diaphoretick and very
Deopilative; [Errata: Deopilative)] Yet I remember _Helmont_[18]
somewhere informes us, that there is this Difference betwixt the
saline spirit of Urine and that of Mans blood, that the former will
not cure the Epilepsy, but the Latter will. Of the Efficacy also of
the Salt of Common Amber against the same Disease in Children, (for in
Grown Persons it is not a specifick) I may elsewhere have an Occasion
to Entertain You. And when I consider that to the obtaining of these
Volatile Salts (especially that of Urine) there is not requisite such
a Destructive Violence of the Fire, as there is to get those Salts
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