1are
poured into the caldron the same number of amphorae of the solution as of
congíi of the lye of which I have already spoken, and into the same caldron
is thrown as much of the already made saltpetre as the solution and lye will
dissolve. As soon as the mixture effervesces and forms scum, it is trans
ferred to a vat, into which on a cloth has been thrown washed sand obtained
from a river. Soon afterward the plug is drawn out of the hole at the
bottom, and the mixture, having percolated through the sand, escapes into
a tub. It is then reduced by boiling in one or another of the caldrons, until
the greater part of the solution has evaporated; but as soon as it is well
boiled and forms scum, a little lye is poured into it. Then it is transferred to
another vat in which there are small rods, to which it adheres and congeals in
two days if there is but little of it, or if there is much in three days, or
at the most in four days; if it does not condense, it is poured back into the
caldron and re-boiled down to half; then it is transferred to the vat to cool.
The process must be repeated as often as is necessary.
congíi of the lye of which I have already spoken, and into the same caldron
is thrown as much of the already made saltpetre as the solution and lye will
dissolve. As soon as the mixture effervesces and forms scum, it is trans
ferred to a vat, into which on a cloth has been thrown washed sand obtained
from a river. Soon afterward the plug is drawn out of the hole at the
bottom, and the mixture, having percolated through the sand, escapes into
a tub. It is then reduced by boiling in one or another of the caldrons, until
the greater part of the solution has evaporated; but as soon as it is well
boiled and forms scum, a little lye is poured into it. Then it is transferred to
another vat in which there are small rods, to which it adheres and congeals in
two days if there is but little of it, or if there is much in three days, or
at the most in four days; if it does not condense, it is poured back into the
caldron and re-boiled down to half; then it is transferred to the vat to cool.
The process must be repeated as often as is necessary.
Others refine saltpetre by another method, for with it they fill a pot
made of copper, and, covering it with a copper lid, set it over live coals, where
it is heated until it melts. They do not cement down the lid, but it has
a handle, and can be lifted for them to see whether or not the melting has taken
place. When it has melted, powdered sulphur is sprinkled in, and if the pot
set on the fire does not light it, the sulphur kindles, whereby the thick, greasy
matter floating on the saltpetre burns up, and when it is consumed the salt
petre is pure. Soon afterward the pot is removed from the fire, and later, when
cold, the purest saltpetre is taken out, which has the appearance of white
marble, the earthy residue then remains at the bottom. The earths from
which the solution was made, together with branches of oak or similar trees,
are exposed under the open sky and sprinkled with water containing saltpetre.
After remaining thus for five or six years, they are again ready to be made
into a solution.
made of copper, and, covering it with a copper lid, set it over live coals, where
it is heated until it melts. They do not cement down the lid, but it has
a handle, and can be lifted for them to see whether or not the melting has taken
place. When it has melted, powdered sulphur is sprinkled in, and if the pot
set on the fire does not light it, the sulphur kindles, whereby the thick, greasy
matter floating on the saltpetre burns up, and when it is consumed the salt
petre is pure. Soon afterward the pot is removed from the fire, and later, when
cold, the purest saltpetre is taken out, which has the appearance of white
marble, the earthy residue then remains at the bottom. The earths from
which the solution was made, together with branches of oak or similar trees,
are exposed under the open sky and sprinkled with water containing saltpetre.
After remaining thus for five or six years, they are again ready to be made
into a solution.
Pure saltpetre which has rested many years in the earth, and that which
exudes from the stone walls of wine cellars and dark places, is mixed with the
first solution and evaporated by boiling.
exudes from the stone walls of wine cellars and dark places, is mixed with the
first solution and evaporated by boiling.
Thus far I have described the methods of making nítrum, which are not
less varied or multifarious than those for making salt. Now I propose to
describe the methods of making alum,10 which are likewise neither all alike,
nor simple, because it is made from boiling aluminous water until it con
denses to alum, or else from boiling a solution of alum which is obtained
from a kind of earth, or from rocks, or from pyrites, or other minerals.
less varied or multifarious than those for making salt. Now I propose to
describe the methods of making alum,10 which are likewise neither all alike,
nor simple, because it is made from boiling aluminous water until it con
denses to alum, or else from boiling a solution of alum which is obtained
from a kind of earth, or from rocks, or from pyrites, or other minerals.