salt liquor, the Spaniards think, as Pliny writes5, that the wood itself turns
into salt. Oak is the best wood, as its pure ash yields salt ; elsewhere hazelwood is lauded. But with whatever wood it be made, this salt is not
greatly appreciated, being black and not quite pure ; on that account this
method of salt-making is disdained by the Germans and Spaniards.
The solutions from which salt is made are prepared from salty earth or
from earth rich in salt and saltpetre. Lye is made from the ashes of reeds
and rushes. The solution obtained from salty earth by boiling, makes salt
only ; from the other, of which I will speak more a little later, salt and saltpetre are made ; and from ashes is derived lye, from which its own salt is
obtained. The ashes, as well as the earth, should first be put into a large
vat ; then fresh water should be poured over the ashes or earth, and it should
be stirred for about twelve hours with a stick, so that it may dissolve the
salt. Then the plug is pulled out of the large vat ; the solution of salt or the
lye is drained into a small tub and emptied with ladles into small vats ;
finally, such a solution is transferred into iron or lead caldrons and boiled,
until the water having evaporated, the juices are condensed into salt. The
above are the various methods for making salt. (Illustration p. 557.)
Nitrum6 is usually made from nitrous waters, or from solutions or from
lye. In the same manner as sea-water or saltwater is poured into salt-pits
and evaporated by the heat of the sun and changed into salt, so the nitrous
Nile is led into nitrum pits and evaporated by the heat of the sun and con-
*Pliny xxxi., 39-40. " In the Gallic provinces in Germany they pour salt water
" upon burning wood. The Spaniards in a certain place draw the brine from wells, which
" they call Muria. They indeed think that the wood turns to salt, and that the oak is the
" best, being the kind which is itself salty. Elsewhere the hazel is praised. Thus the char" coal even is turned into salt when it is steeped in brine. Whenever salt is made with wood it
" is black."
eWe have elsewhere in this book used the word " soda " for the Latin term nitrum,
because we believe as used by Agricola it was always soda, and because some confusion
of this term with its modern adaptation for saltpetre (nitre) might arise in the mind of the
reader. Fortunately, Agricola usually carefully mentions other alkalis, such as the product
from lixiviation of ashes, separately from his nitrum. In these paragraphs, however, he has
soda and potash hopelessly mixed, wherefore we have here introduced the Latin term.
The actual difference between potash and soda—the nitrum of the Ancients, and the alkali
of Geber (and the glossary of Agricola), was not understood for two hundred years after
Agricola, when Duhamel made his well-known determinations ; and the isolation of sodium
and potassium was, of course, still later by fifty years. If the reeds and rushes described
in this paragraph grew near the sea, the salt from lixiviation would be soda, and likewise
the Egyptian product was soda, but the lixiviation of wood-ash produces only potash ; as
seen above, all are termed nitrum except the first.
Historical Notes.—The word nitrum, nitron, nitri, neter, nether, or similar
forms, occurs in innumerable ancient writings. Among such references are Jeremiah (n., 22)
Proverbs (xxv., 20), Herodotus (n., 86, 87), Aristotle {Prob. 1., 39, De Mirab. 54), Theophrastus (De Igne 435 ed. Heinsii, Hist. Plants m., g), Dioscorides (v., 89), Pliny (xiv., 26,
and xxxi., 46). A review of disputations on what salts this term comprised among the
Ancients would itself fill a volume, but from the properties named it was no doubt mostly
soda, more rarely potash, and sometimes both mixed with common salt. There is every
reason to believe from the properties and uses mentioned, that it did not generally comprise nitre (saltpetre)—into which superficial error the nomenclature has led many translators.
The preparation by way of burning, and the use of nitrum for purposes for which we now
use soap, for making glass, for medicines, cosmetics, salves, painting, in baking powder,
for preserving food, embalming, etc., and the descriptions of its taste in " nitrous " waters,—
all answer for soda and potash, but not for saltpetre. It is possible that the common occurrence of saltpetre as an efflorescence on walls might naturally lead to its use, but in any
event its distinguishing characteristics are nowhere mentioned. As sal-ammoniac occurred
