potassium carbonate (vegetable alkali). This gave potassium sulphate (Alkali veg.
vitr.)
6 as a by-product which was not very useful. Scheele’s method was to first treat
magnesium sulphate solution with sodium chloride; from the solution sodium
sulphate (Sal Glauberi) could be crystallised in the cold leaving magnesium
chloride in solution. Sodium sulphate was far more useful than potassium sulphate.
The stoichiometry in Scheele’s procedure is quite accurate; for 1 mol of sodium
chloride, he used 0.49 magnesium sulphate. The yield of sodium sulphate was
around 34–48%.
Scheele noted that the operation had to be performed in the winter; in the
summer it would invariably fail. At room temperature, a solution prepared
according to Scheele’s instructions is unsaturated. Furthermore, sodium sulphate is
prone to form highly supersaturated solutions. The author of this book found that
such a solution could be kept for hours at −18 °C without crystallisation. Upon
seeding with sodium sulphate dekahydrate, it readily crystallises at 0 °C. Finally,
Magnesia alba was precipitated in the usual manner from the magnesium chloride
solution by the addition of an excess of potassium carbonate.
Bergman also studied Magnesia alba in a dissertation published in 1775 [16].
Bergman’s objectives were, however, different than those of Scheele, and Bergman’s work brought forward new evidence of the elemental nature of Magnesia and
was of little interest for a pharmacist.
27.5 Other Works by Scheele Related to Medicine
In addition to the papers related to the pharmacopoeia, Scheele published two more
papers where he was consulted in medicinal questions. Shortly prior to his death,
Scheele wrote a letter to Bergius, which was subsequently published [17]. This
letter reports the analysis of a medicine sent to him by the influential businessman
Abraham Grill (1719−1799), who used the medicine to treat venereal diseases
among his staff. The medicine was imported at great expense from Amsterdam, and
Grill was keen to know if it could be prepared at a lower cost. Scheele found it to be
a solution of mercury(II) chloride and iron(II) chloride and gave a recipe for its
preparation [18]. Mercury, although toxic to humans, was a common cure for
syphilis.
A second letter, also written to Bergius and subsequently published, Scheele [19]
concerned a device for oxygen treatment of tuberculosis patients. Bergius and his
colleague surgeon Herman Schützercrantz (1713−1802) was treating an apparently
very wealthy and important but unnamed lady with oxygen delivered in small
amounts from a pharmacy in Stockholm. The problem was that the patient wanted
to be able to breathe oxygen for prolonged times, and a method for preparation of
oxygen on a large scale was needed. Scheele suggested building an airtight cupboard connected to a retort where potassium nitrate (saltpetre) was heated [20].
6
Note that Scheele is using Bergman’s nomenclature.
27.4 A New Method for Preparing Magnesia alba
371
vitr.)
6 as a by-product which was not very useful. Scheele’s method was to first treat
magnesium sulphate solution with sodium chloride; from the solution sodium
sulphate (Sal Glauberi) could be crystallised in the cold leaving magnesium
chloride in solution. Sodium sulphate was far more useful than potassium sulphate.
The stoichiometry in Scheele’s procedure is quite accurate; for 1 mol of sodium
chloride, he used 0.49 magnesium sulphate. The yield of sodium sulphate was
around 34–48%.
Scheele noted that the operation had to be performed in the winter; in the
summer it would invariably fail. At room temperature, a solution prepared
according to Scheele’s instructions is unsaturated. Furthermore, sodium sulphate is
prone to form highly supersaturated solutions. The author of this book found that
such a solution could be kept for hours at −18 °C without crystallisation. Upon
seeding with sodium sulphate dekahydrate, it readily crystallises at 0 °C. Finally,
Magnesia alba was precipitated in the usual manner from the magnesium chloride
solution by the addition of an excess of potassium carbonate.
Bergman also studied Magnesia alba in a dissertation published in 1775 [16].
Bergman’s objectives were, however, different than those of Scheele, and Bergman’s work brought forward new evidence of the elemental nature of Magnesia and
was of little interest for a pharmacist.
27.5 Other Works by Scheele Related to Medicine
In addition to the papers related to the pharmacopoeia, Scheele published two more
papers where he was consulted in medicinal questions. Shortly prior to his death,
Scheele wrote a letter to Bergius, which was subsequently published [17]. This
letter reports the analysis of a medicine sent to him by the influential businessman
Abraham Grill (1719−1799), who used the medicine to treat venereal diseases
among his staff. The medicine was imported at great expense from Amsterdam, and
Grill was keen to know if it could be prepared at a lower cost. Scheele found it to be
a solution of mercury(II) chloride and iron(II) chloride and gave a recipe for its
preparation [18]. Mercury, although toxic to humans, was a common cure for
syphilis.
A second letter, also written to Bergius and subsequently published, Scheele [19]
concerned a device for oxygen treatment of tuberculosis patients. Bergius and his
colleague surgeon Herman Schützercrantz (1713−1802) was treating an apparently
very wealthy and important but unnamed lady with oxygen delivered in small
amounts from a pharmacy in Stockholm. The problem was that the patient wanted
to be able to breathe oxygen for prolonged times, and a method for preparation of
oxygen on a large scale was needed. Scheele suggested building an airtight cupboard connected to a retort where potassium nitrate (saltpetre) was heated [20].
6
Note that Scheele is using Bergman’s nomenclature.
27.4 A New Method for Preparing Magnesia alba
371