separated. To obtain the amount of calcium in the sample, the amount of calcium
carbonate added for neutralisation had to be subtracted.
From the second part of the solution, iron was precipitated as Prussian blue with
potassium hexacyanoferrate and aluminium precipitated with magnesium carbonate. A similar protocol was used for the analysis of asbestos, although asbestos is
insoluble in acids and thus had to be fused with alkali to become soluble [44].
23.5 Bergman and the Blow-Pipe
Since centuries, metal workers had used a bent metal tube—a so-called blow-pipe
—to achieve high temperatures for welding and brazing. The principle was simple:
a stream of air was blown from the mouth through the tube into the flame of a lamp
or a candle. The extra oxygen increased the temperature. The use of blow-pipes was
adopted by glass-blowers and in a book on glass blowing, Ars vitraria, Kunckel
introduced the idea of using the blow-pipe for chemical research in 1689: “There
are even some other possibilities in this. Especially in the workshop of a chemist, it
can be used for many things. I will just mention this among other things: It often
happens that one has a small amount of metallic calx, or something similar, and
wants to melt it and see what metal it contains. It can in no way be made easier than
this, that one just takes a piece of charcoal, makes a cavity in it and takes the calx,
or whatever one wants to melt, and puts it inside, and with the tube blows the flame
of a strong candle against it” [45]. It appears to have been Stahl who first put this
into practice and he was soon followed by Johann Cramer (1710–1770), Marggraf,
Pott and von Swab [46]. According to Bergman, it was Swab who first used the
blow-pipe for analysis of minerals in c. 1738 [47]. It is likely that Swab taught the
method to Cronstedt, who frequently referred to it in his classical Försök til Mineralogie (An attempt to a mineralogy) in 1758, but without explaining the procedure. When von Engeström translated Cronstedt’s book to English in 1765, he
added an essay describing the use of the blow-pipe. Due to the influence from Swab
and Cronstedt, the blow-pipe became very popular in Sweden and was used by
Rinman and Qvist; although certainly not unknown, the blow-pipe found considerably less use on the continent. In the hands of chemists, the blow-pipe developed
from a simple bent tube to include a spherical compartment to collect moister that
otherwise condensed in the tube (Fig. 23.2). Bergman improved the design of the
blow-pipe even further; he used a blow-pipe made of silver alloyed with a small
amount of platinum. Rather than a spherical bulb to collect moister, Bergman’s
blow-pipe used a small box (Fig. 23.3).
One can suspect that it was Rinman or possibly Swab who taught Bergman how
to use the blow-pipe. Bergman made extensive use of the blow-pipe and wrote a
manual, De tubo feruminatorio, which he sent to von Born in Vienna in 1777,
where it was published in 1779. According to Thomson, who had met Gahn, the
experiments were performed by Gahn on Bergman’s request [48]. This is not
improbable, as Gahn was known to be a master of the blow-pipe but very reluctant
324
23 Bergman as an Analytical Chemist
carbonate added for neutralisation had to be subtracted.
From the second part of the solution, iron was precipitated as Prussian blue with
potassium hexacyanoferrate and aluminium precipitated with magnesium carbonate. A similar protocol was used for the analysis of asbestos, although asbestos is
insoluble in acids and thus had to be fused with alkali to become soluble [44].
23.5 Bergman and the Blow-Pipe
Since centuries, metal workers had used a bent metal tube—a so-called blow-pipe
—to achieve high temperatures for welding and brazing. The principle was simple:
a stream of air was blown from the mouth through the tube into the flame of a lamp
or a candle. The extra oxygen increased the temperature. The use of blow-pipes was
adopted by glass-blowers and in a book on glass blowing, Ars vitraria, Kunckel
introduced the idea of using the blow-pipe for chemical research in 1689: “There
are even some other possibilities in this. Especially in the workshop of a chemist, it
can be used for many things. I will just mention this among other things: It often
happens that one has a small amount of metallic calx, or something similar, and
wants to melt it and see what metal it contains. It can in no way be made easier than
this, that one just takes a piece of charcoal, makes a cavity in it and takes the calx,
or whatever one wants to melt, and puts it inside, and with the tube blows the flame
of a strong candle against it” [45]. It appears to have been Stahl who first put this
into practice and he was soon followed by Johann Cramer (1710–1770), Marggraf,
Pott and von Swab [46]. According to Bergman, it was Swab who first used the
blow-pipe for analysis of minerals in c. 1738 [47]. It is likely that Swab taught the
method to Cronstedt, who frequently referred to it in his classical Försök til Mineralogie (An attempt to a mineralogy) in 1758, but without explaining the procedure. When von Engeström translated Cronstedt’s book to English in 1765, he
added an essay describing the use of the blow-pipe. Due to the influence from Swab
and Cronstedt, the blow-pipe became very popular in Sweden and was used by
Rinman and Qvist; although certainly not unknown, the blow-pipe found considerably less use on the continent. In the hands of chemists, the blow-pipe developed
from a simple bent tube to include a spherical compartment to collect moister that
otherwise condensed in the tube (Fig. 23.2). Bergman improved the design of the
blow-pipe even further; he used a blow-pipe made of silver alloyed with a small
amount of platinum. Rather than a spherical bulb to collect moister, Bergman’s
blow-pipe used a small box (Fig. 23.3).
One can suspect that it was Rinman or possibly Swab who taught Bergman how
to use the blow-pipe. Bergman made extensive use of the blow-pipe and wrote a
manual, De tubo feruminatorio, which he sent to von Born in Vienna in 1777,
where it was published in 1779. According to Thomson, who had met Gahn, the
experiments were performed by Gahn on Bergman’s request [48]. This is not
improbable, as Gahn was known to be a master of the blow-pipe but very reluctant
324
23 Bergman as an Analytical Chemist