It should be mentioned that it was by the examination of Epsom salts that Black was led to his epoch-making discovery of the distinction between the alkaline earths, and also of fixed air, in 1754.
In Quincy's "Dispensatory" (1724), medicinal waters like those of Epsom are described as Aquæ Aluminosæ. It is stated that there are many in England, scarce a county without them. The principal ones about London are at Epsom, Acton, Dulwich, and North-hall. They all "abound with a salt of an aluminous and nitrous nature," and "greatly deterge the stomach and bowels." But it is easy to take them too frequently, so that "the salts will too much get into the blood, which by their grossness will gradually be collected in the capillaries and glands to obstruct them and occasion fevers." After some more advice Quincy adds—
"It is difficult to pass this article without setting a mark upon
that abominable cheat which is now sold by the name of Epsom
waters. Dr. Grew, who was a most worthy physician and an industrious
experimenter, made trial how much salt these waters
would leave upon evaporation, and found that a gallon left about
two drams, or near, according to my best remembrance, for I have
not his writings by me. He likewise found the salt thus procured
answered the virtues of the water in its cathartic qualities. Of
this an account was given before the Royal Society in a Latin
dissertation. But the avaricious craft of a certain furnace-philosopher
could not let this useful discovery in natural knowledge
rest under the improvement and proper use of persons of integrity;
but he pretended to make a great quantity for sale; and to recommend
his salt translated the Doctor's Lecture into English to give
away as a quack-bill."
Quincy proceeds to tell us how other competitors
came in, and how the price was so reduced that what
was first sold at one shilling an ounce, and could not
honestly be made under (Quincy apparently refers to
the salt made by evaporation), came down in a short
time to thirty shillings per hundredweight.
