Lavoisier and Sage on Potash Production

This is reading notes from the accessible potash document I described in this post.

Sage et al (p.1) note that potash smells acidic and like urine. It usually is dark brown in coloration (p.2), when it is in its coarse state. When fired in the reverberatory furnace, it turns slate blue or white and is now called potash (p.2). When potash is calcined well [i.e. turns into pearl ash, RCK], it becomes porous and light, like pumice (p.3).

The most common method for potash production is to burn wood (p.5) and put the ashes into a copper vessel, adding water and boiling the mixture. One lets the lye settle, decants it into a separate boiler, then lets the remaining water evaporate until the potash is dry.

In places of charcoal production, stovepipes can be used to gather up the humidity distilled out of the charring wood pile into basins, which are then evaporated using boilers (p.6). If the salts sticks too strongly to the pans, scissors and mallets are used to detach it (p.7).  All woods produce some salts, but some more than others. Older ashes produce more, provided they are kept wet, and the best come from hardwoods (p.7). In the summer, they use cold water; in the winter, they mix hot and cold water half-and-half. Water that is too hot spoils the process, as the grease cannot separate from the salts. Stagnant waters give twice the potassium than clear waters.

One places wooden troughs of oak or pine a finger and a half apart, with a false bottom, where one places a bed of straw, and masses the ashes on top of that, so that the water cannot drain too quickly (p.8). One replaces the straw every six weeks in winter, and in the summer only every two months. Once the liquid stops fuming, one has to stir it with a stick, let the fire go out and cut the salt out with sticks.

The best method is the Swedish method, where one cuts the wood into pieces and piles it up.

L'art de fabriquer le salin et la potasse

I am still trying to figure out the relationship between

L'art de fabriquer le salin et la potasse ; suivi des Expériences sur les moyens de multiplier la fabrication de la potasse ([Reprod.]) / par le citoyen Pertuis, & par le citoyen B. G. Sage... (Bavarian library copy) and the Lavoisier article from 1779 with the same title (catalog entry). Earlier I confused the Lavoisier book with this article on just Salpeter production, which Lavoisier also wrote when a regisseur at the poudre commission.

At first I thought that Pertuis and Sage were regisseurs with Lavoisier, but that seems unlikely based on this essay. At the same time, the name and the structure look so similar, that one suspects it might be a reprint, cleansed for the Republic (as the labels citoyen make one suspect).

One thing is certain: Lavoisier was executed in 1794.

Prof Marco Beretta of the University of Bologna, in a private communication, pointed out [typos rectified, RCK], that L'art de fabriquer le salin et la potasse was

... originally published anonymously upon a report made by Tillet, Cadet, Sage and Lavoisier. The report was probably written and conducted by Lavoisier. In the second ed. the experiments by Pertuis were added and for [from?] the index it seems that a few experiments by Sage were also added to the original ones. Thus, although Sage and Pertuis claim to be the author of the whole work[, this] was misleading to say the least, [but] their additions, apparently not particularly significant, justified the appearance of their names on the frontispiece.

However, an analytical comparison of the two editions remains a desideratum.

Potash and Pioneering in the US of A

In his 1951 article Origin and Occurrence of Commercial Potash Deposits in the Proceeding of the Academy of Science of Oklahoma, Volume 32, Section D, p.123-125, Robert Fite gives a one paragraph summary of potash production before 1850 in the US of A (1851 was the year the Germans discovered natural or geological potash in Strassfurt).

Potash has been an important item of commerce for centuries. Until recently, its use was restricted to the manufacture of soap, glass, and black gunpowder. The salt was obtained by leaching ashes of wood and other vegetative wastes tn large iron pots-hence, the name "potash," It became the principal product of the chemical Industries in America before 1850 as a byproduct of clearing the virgin forest lands for agriculture. The total annual supply for these chemical uses, however, never amounted to more than a few thousand tons for the entire world. (p.123)

As far as the production is concerned, the American Academy of Sciences ran a short article in 1793 that may be relevant to this, Aaron Dexter, Observations on the Manufacture of Pot Ash [sic!],  in: Memoirs of the American Academy of Arts and Sciences, Vol. 2, No. 1 (1793), pp. 165-170.

First of all, the book repeats the information given by Mark L. Staker in his Whitney in Ohio article for BYU Studies 42.1 (2003), pp.75ff. So this makes it likely that when Staker speaks about "manuals", he had something this information in mind.

Dexter argues that quality of the potash needs to be improved (p.165) and that this low quality is not the fault of either the equipment or the impurities (p.166), but rather of the technique.

Too often, not all of the salts are extracted from the ashes.

For this purpose, rain or river water ought always to be preferred. The ashes should be saturated, and remain with about an inch of water over the top of them for twelve hours at least. (p.166)

By straining the leach out of the tub, either with a small hole or a false bottom, so that none of the ashes can escape, water can be continuously replenished. The lies needs to be boiled

... until they are so reduced in strength, as they will no longer pay the expense of boiling. The ashes however, still to be preserved; and fresh water applied as before. And when drawn off, they may be used with profit on fresh ashes, as long as there remain in the lies any salts, which may be discovered by the taste. (p.166-167)

Next, Dexter recommends double-filtering the lie, as it exits the tub and as it enters the receiver. Then it needs to sit for 24 hours. When transferred into the kettle, the sediment needs to be left behind in the receiver (p.167).

Every precaution should be taken to let nothing fall into the lies previous to, and whilst boiling. Therefore, that injurious practice of laying wood on the kettles for drying must be avoided. (p.167)

[[RCK: it is hard to believe that putting wood on the kettles did dry them instead of steaming them.]]

The first drawn lie should be boiled down to half; later lies even more so. At that point, lime can be added, though mixing the lie into the ashes is fine too.

The lie should now cool off to the point that it is body temperature ("to the state of blood heat" (p.167)), and again there will be sedimentation,  a "chalky earth", which needs to be detained. Once the earthy matters and the common salt (p.168) have been removed, using the same process as salpeter production uses for the common salt, the lie is ready to be fluxed. This involves boiling the lie down completely (p.168). Then the fire is increased to "for the purpose of destroying the inflammable substance" (p.169). Dexter provides a sliver-based test for evaluating the quality of the potash, which is re-dissolved in water and then a silver coin turned dark or black with it if the "inflammable substance" has not been removed. If the potash contains the "inflammable substance", then either re-dissolving in pure water and re-fluxing is required; or the potash is turned into "pearl ashes ... by calcination" (p.169).

Dexter knows that the process is discouragingly long, believes that the cleaned lie not only fluxes faster, but that the superior quality of the potash with fetch a better price (pp.169-170).

Dexter closes with the observation (p.170), that the importance of the subject matter, since potash production is even discussed by legislatures, and the need to be comprehensible to the business people and workers who produce the chemical, have led him to write the article in the straight-forward language chosen. (As an example, on (p.169), Dexter uses the term "oily substance" as an analogon for his "inflammable substance", because that is the term the workers use.)