to another difficulty, if by nitre we mean
saltpetre, for that will, as we all know, preserve animal tissue for a
certain time; however, I do not think we can translate natron as being
nitre (saltpetre), for in former days many salts were included under
the general term nitre; for instance, our common soda and potash, the
chemical composition of which was unknown until Davy, in 1807,
extracted the metals sodium and potassium from those salts. Boitard
expressly states:

"Il parait que ce natrum etait un alkali fixe, et pas du tout du nitre
comme quelques auteurs l'ont pense; ce qui semblerait appuyer cette
opinion, c'est que lea femmes egyptiennes se servaient de natrum pour
faire leur lessive, comme on as sert aujourd'hui de la soude."

In Peru the soil may be said to be impregnated with nitre, but that is
nitrate of soda, and not really saltpetre (nitrate of potassium), as
many people imagine who hear it called simply nitre.

Mr. Thos. W. Baker, who has most obligingly unearthed several old
works for me, says:

"Now I think of it, natron is perfectly familiar to me as apparently a
mixture of broken soda crystals and a brown earth which is sold in the
bazaars of India, under the name of 'sootjee moogee,' for domestic
purposes; and I know, from experience, that unless it is washed off
paint work directly it is passed over it with a cloth all the paint
comes off bare, sometimes to the wood."

Again, he says:

"In Bayley's Dictionary, circa 1730, I find the following: 'Natron;
or, a Natron, from Gr. Natron (?), a kind of black greyish salt, taken
out of a lake of stagnant water in the territory of Terrana, in
Egypt."

Also see "Penny Cyclopaedia," vol. xvi, p. 105, "Natron, native
sesquicarbonate of soda (see 'Sodium'):"

"The Natron Lakes, which are six in number, are situated in a valley
bordering upon Lower Egypt, and are remarkable for the great quantity
of salt which they produce. The crystallisations are both of muriate
of soda (or common salt) and of carbonate of soda. ... The 'Natron' is
collected once a year, and is used both in Egypt and Syria, as also in
Europe, for manufacturing glass and soap, and for bleaching linen."

Turning to "Sodium" for the sesquicarbonate, which is found native in
Hungary, and also near Fezzan, in Africa:

'By the natives it is called "Trona." It is found in hard striated
crystalline masses, and is not altered by exposure to the air, but is
readily soluble in water. This s