Salts had a distinguishable taste and needed no more than 500 times their weight
of water to dissolve (Bergman had stated 200 times in The Chemical Lectures of H.
T. Scheffer). Water was “finer and more penetrating” at higher temperature, and thus
the solubility of salts increased with temperature. While discussing the solubility,
Bergman seems to have confused the concepts of solubility and rate of dissolution.
Bergman then discussed the classification of salts after the same system that he
presented in The Chemical Lectures of H.T. Scheffer.
Earths could be divided into primitive and compounded earths; five primitive
earths were known corresponding to what we call the oxides of calcium, magnesium, barium, aluminium and silicon. The chemical similarity of calcium and
barium was pointed out by Bergman. In addition, there were reasons to suspect a
new earth, “earth of gems” to be present in diamonds (see Sect. 23.4).
In the introduction to the passage on combustible materials, Bergman introduced
the concept of phlogiston: it was the cause of combustibility, but it was so fine and
sublime that it eluded all our senses. Still it could be transferred between different
bodies and was probably a component in all substances. The rest of the section is
very similar to the corresponding section in The Chemical Lectures of H.T. Scheffer,
discussing sulphur, phosphorus, oils, ether, alcohol and gunpowder.
Metals were shiny, opaque bodies heavier than all other bodies with densities
between 6 and 20 times the density of water. They all consisted of phlogiston and
particular earths, called metal calces. Metals in which the attraction between the
calx and phlogiston was so strong that they could not be separated by fire, were
called noble metals; they were gold, platinum and silver. Bergman discussed the
melting points of alloys, and was surprised that certain mixtures of metals have
lower melting points than the pure constituents (thus referring to what we call
eutectic mixtures
2 ). His claim that “all metals combine with sulphur except gold
and zinc” is very difficult to understand for anyone who has explored the violent
reaction between powdered zinc and flowers of sulphur. Also, zinc is commonly
found in nature as zinc blende, ZnS. After discussing arsenic acid, he introduced his
theory that all metal calces actually are metallic acids combined with phlogiston
(Sect. 15.4). Bergman noted that metals do not dissolve in acids without the loss of
phlogiston, meaning that they have to be oxidised.
When discussing water, he discussed his atomistic view of matter (Sect. 22.3):
all liquids were composed of infinitesimally small particles. On cooling water to
0 °C, the particles lost their mobility and the water froze. Although Bergman
supported the material view of heat, this statement brought him quite close to the
truth (in the section on air, however, he clearly stated that “heat is not motion”). The
claim that the volume increases 14,000 times when water turns to steam may simply
be a printing error (the true value is 1,700). He also took the opportunity to discuss
the highly debated question whether water can turn into earth and wrote that there
were no proofs for such observations, but that it was not improbable.
2
A eutectic mixture is a homogenous mixture which has a lower melting point than the pure
components, such as soldering lead and the anti-freezing mixture of water and ethylene glycol used
in car engines.
11.2 Instructions to the Lectures on the Nature and Benefit of Chemistry
169
of water to dissolve (Bergman had stated 200 times in The Chemical Lectures of H.
T. Scheffer). Water was “finer and more penetrating” at higher temperature, and thus
the solubility of salts increased with temperature. While discussing the solubility,
Bergman seems to have confused the concepts of solubility and rate of dissolution.
Bergman then discussed the classification of salts after the same system that he
presented in The Chemical Lectures of H.T. Scheffer.
Earths could be divided into primitive and compounded earths; five primitive
earths were known corresponding to what we call the oxides of calcium, magnesium, barium, aluminium and silicon. The chemical similarity of calcium and
barium was pointed out by Bergman. In addition, there were reasons to suspect a
new earth, “earth of gems” to be present in diamonds (see Sect. 23.4).
In the introduction to the passage on combustible materials, Bergman introduced
the concept of phlogiston: it was the cause of combustibility, but it was so fine and
sublime that it eluded all our senses. Still it could be transferred between different
bodies and was probably a component in all substances. The rest of the section is
very similar to the corresponding section in The Chemical Lectures of H.T. Scheffer,
discussing sulphur, phosphorus, oils, ether, alcohol and gunpowder.
Metals were shiny, opaque bodies heavier than all other bodies with densities
between 6 and 20 times the density of water. They all consisted of phlogiston and
particular earths, called metal calces. Metals in which the attraction between the
calx and phlogiston was so strong that they could not be separated by fire, were
called noble metals; they were gold, platinum and silver. Bergman discussed the
melting points of alloys, and was surprised that certain mixtures of metals have
lower melting points than the pure constituents (thus referring to what we call
eutectic mixtures
2 ). His claim that “all metals combine with sulphur except gold
and zinc” is very difficult to understand for anyone who has explored the violent
reaction between powdered zinc and flowers of sulphur. Also, zinc is commonly
found in nature as zinc blende, ZnS. After discussing arsenic acid, he introduced his
theory that all metal calces actually are metallic acids combined with phlogiston
(Sect. 15.4). Bergman noted that metals do not dissolve in acids without the loss of
phlogiston, meaning that they have to be oxidised.
When discussing water, he discussed his atomistic view of matter (Sect. 22.3):
all liquids were composed of infinitesimally small particles. On cooling water to
0 °C, the particles lost their mobility and the water froze. Although Bergman
supported the material view of heat, this statement brought him quite close to the
truth (in the section on air, however, he clearly stated that “heat is not motion”). The
claim that the volume increases 14,000 times when water turns to steam may simply
be a printing error (the true value is 1,700). He also took the opportunity to discuss
the highly debated question whether water can turn into earth and wrote that there
were no proofs for such observations, but that it was not improbable.
2
A eutectic mixture is a homogenous mixture which has a lower melting point than the pure
components, such as soldering lead and the anti-freezing mixture of water and ethylene glycol used
in car engines.
11.2 Instructions to the Lectures on the Nature and Benefit of Chemistry
169