Perhaps the foda and falicornia may thrive better
when nurtured by fait water, but it is no lefs certain that
the alkaline bafis of common fait is found formed in
thefe two plants, and in many others as well as in the
barilla, which is fowed in many parts of Spain, where
they make as good foap as that famous fort at Alicant
made with foda and falicornia. With refpect to neutral
falls, there are at leaft five fubftances, in which they
are found, viz. earth, plants, fait water, mineral, and
artificial fubftances.
After this digreffion, let us now fee howfaltpetre is generally
made in France and in Spain, I fay nothing of England
or Holland, becaufe they make none, importing what
they want from the Eaft Indies, where it is found naturally
in the earth, as in Spain, where I have feen falt-
petre made with the lixivium of nitrous earth, colleded in
places where perhaps there never was a tree nor a plant.
In Paris they haye feventeen faltpetre works : every
thing that is carried on there, as well as in other parts
of the kingdom, is done according to royal ordinances,
in the manner I am going to relate : The rubbifh and
filth of old houfes is carried to the works, and pounded
with hammers ; the dull is then put into calks, perforated
at bottom, the aperture covered with ftraw, to
give
give a free paffage to the liquor. Water is then poured
on this dull, which in its palfage carries away all the fa-
line matter. This impregnated matter is called a lye,
which if they were at that period to boil, would produce
faltpetre o f a greafy nature; to remedy this, they pur-
chafe the afhes of all the wood fires in Paris,; from which
they alfo draw a lye that -is mixed with the former, then
boil up the whole (a). In proportion as the water evaporates,
the common fait which cryftalizes when hot,
foon falls to the bottom o f the cauldron, and the faltpetre,
which only cryftalizes when cool, remains diffolved
in the water. They draw off this water, loaded with
faltpetre, into other veffels, and place, it in. the ihade,:
where the nitre cryftalizes. This is called faltpetre of
the firft boiling, having ftill fome remains o f common
fait, earth, and greafy matter, incorporated with i t ; it
is conveyed to the arfenal to be properly refined, being
boiled over again, and left to cryftalize two or three
timys, or more if found neceffary ; by which, means it
i s cleared o f all its impurities, and becomes perfectly
adapted to the making o f gunpowder and the other ufes:
to which it is applied in the arts,; hu,t for medical pur-
pofes5 it muff undergo another purifications . Thofe'who
(«) The fad teems to be this ; the Alt they obtain from the lye of the ntbbilh, is a nitre
“ " " h7 baGs’ lhe fixed ^ ¿ ’le alkali procured from the wood aihes is then added ,
kah * S fflW » .a p d ; and taking its place; forms trtie Alt-
F are