L E T T E R IV .
The method o f making Saltpetre in Spain.
IN the year 1754, I received orders (a) from the mi-
niftry to infpeX into feveral faltpetre works, as well
as into the making of gunpowder, which having complied
with, the following reflexions occurred to my
mind,
All the profeifors o f chemiftry I had converfed with,
either in France or in Germany, laid down as a fixed
principle, that there are three mineral acids in nature :
that the vitriolic, is the univerfal one, belonging to metals,
from whence the other two arife. That the nitrous
is fécond in aXivity, and belongs to the vegetable kingdom,
and the marine being the weakeft o f all, is homogeneous
to fiih. They do not include the animal acid,
which united with the phlogifton (¿), forms the phofpho-
rus. I was further taught, that the fixed alkali of fait-
(à) I)on Guillermo Bowles.
|§ By phlogifton, chemifts mean the moft pure and fimple inflammable principle^ concerning.
which there are a great variety o f opinions and dotftrines, fupported on the one handj
and controverted on the other with equal ingenuity, by chemical writers»
petre,
petre, did not exifl: purely, and limply in nature, but
was generated by fire, and when they found faltpetre,
to be dug out o f the earth naturally in the Ealt Indies,
they thought to fave the difficulty, by faying it proceeded
from the incineration o f woods, which had impregnated
the earth, with this fixed alkali, the bafis o f faltpetre
; fo that I had been led to believe, it was formed
by certain combinations, that took place in the aX o f
combuftion; but I foon found my error,* when I had
had feen the method o f making faltpetre in the different
prpvinces of Spain. I have now evident proofs that the
bafis o f nitre really exifts in the earth and in plants, the.
fame as in the Soda o f Alicant. Let thefe learned gentlemen
come to Spain, they may convince themfelves o f
this truth, and fee faltpetre with its alkaline bafis, in the
manufaXures of Cailile, Aragon, Navarre, Valencia,.
Murcia, and Andalufia, where it is made without the af-
fiftance of vegetable matter ; fometimes throwing in a
handful o f alhes o f matweed, merely to filter the lye of
earth, and though they often meet with gypfeous ftone in
the neighbourhood o f their works, yet they make excellent
faltpetre by boiling the lixivium o f their lands only,
in which they do not find an atom of gypfum ; confe-
qnently they have gunpowder in Spain, without being
indebted for its fixed alkali,., to the vegetable kingdom,
and without the vifible or fenfible converfion of the vitriolic
acid o f gypfum into the nitrous.
E Having