Bergman had received another sample from Black via Schwediauer, which he had
examined. At the end of the paper, Bergman mentioned, for the first time in
Swedish, the isolation of metallic tungsten by the d’Elhuyar brothers (Sect. 15.5).
He also mentioned the mineral (cerite) which Cronstedt had classified as a form of
tungsten, which was chemically unrelated to tungsten. The discovery of cerium in
this mineral would, however, have to wait until the analysis by Berzelius and
Hisinger in 1803. Bergman also discussed, for the last time, the zeolites. These are
porous minerals that have received widespread use today for large varieties of
applications such as absorption and separation of molecules and catalysis.
25.4 Mineralogical Dissertations
A number of dissertations on mineral analysis and related subjects were defended
by Bergman’s students, and probably written by Bergman himself, although the
authorship is difficult to establish. In June 1774, Peter Jacob Hjelm defended a
thesis titled Chemical and Mineralogical Dissertation on White Iron Ores [8]. The
dissertation is written in Swedish, and as Bergman’s dissertations were typically
written in Latin, the choice of language might suggest that the author is Hjelm. The
thesis describes white iron minerals, i.e. minerals where iron occurs as iron(II) and
lacks the dark colours of most iron(III) compounds. When exposed to air, these
minerals darkened (due to oxidation to iron(III)) and finally disintegrated into black
powders. The minerals effervesced with acids in the same way as lime stone, and
the gas evolved was found to be carbon dioxide (aerial acid). All examined specimens were found to contain aerial acid, water, iron, lime and Magnesia nigra
(manganese), and thus seem to be ankerite, Ca(Fe,Mg,Mn)(CO 3 ) 2 . Another
example of a white iron ore is siderite, FeCO 3 .
A dissertation on zinc ores was defended by Geijer in 1779 [9]. It contains a
historical introduction, as did many of Bergman’s works (according to Partington,
Bergman often relied on Pott as a source of historical information [10]), followed
by analysis and discussion of different types of zinc ores. In a 1782 dissertation on
lithomerge, a kaolinite clay mineral, Bergman found a method of selectively precipitating aluminium carbonate with magnesium carbonate from a solution of the
clay in sulphuric acid [11]. This method of separating different kinds of earths also
came to good use in a dissertation on asbestos defended the same year (Sect. 11.4).
Bergman and his student Robsahm analysed 13 different varieties of asbestos [12],
which were found to be composed of lime, magnesia, clay, silica and calx of iron,
i.e. oxides of calcium, magnesium, aluminium, silicon and iron.
2 From a letter to
Bergman from Scheele, dated in May 1782, it is clear that Bergman had asked
Scheele to analyse asbestos, but that Scheele had found no time to do so.
2
Asbestos is a heterogeneous group of fibrous minerals. They are all silicates of elements like
calcium, magnesium and iron.
25.3 Mineralogial Remarks
345
examined. At the end of the paper, Bergman mentioned, for the first time in
Swedish, the isolation of metallic tungsten by the d’Elhuyar brothers (Sect. 15.5).
He also mentioned the mineral (cerite) which Cronstedt had classified as a form of
tungsten, which was chemically unrelated to tungsten. The discovery of cerium in
this mineral would, however, have to wait until the analysis by Berzelius and
Hisinger in 1803. Bergman also discussed, for the last time, the zeolites. These are
porous minerals that have received widespread use today for large varieties of
applications such as absorption and separation of molecules and catalysis.
25.4 Mineralogical Dissertations
A number of dissertations on mineral analysis and related subjects were defended
by Bergman’s students, and probably written by Bergman himself, although the
authorship is difficult to establish. In June 1774, Peter Jacob Hjelm defended a
thesis titled Chemical and Mineralogical Dissertation on White Iron Ores [8]. The
dissertation is written in Swedish, and as Bergman’s dissertations were typically
written in Latin, the choice of language might suggest that the author is Hjelm. The
thesis describes white iron minerals, i.e. minerals where iron occurs as iron(II) and
lacks the dark colours of most iron(III) compounds. When exposed to air, these
minerals darkened (due to oxidation to iron(III)) and finally disintegrated into black
powders. The minerals effervesced with acids in the same way as lime stone, and
the gas evolved was found to be carbon dioxide (aerial acid). All examined specimens were found to contain aerial acid, water, iron, lime and Magnesia nigra
(manganese), and thus seem to be ankerite, Ca(Fe,Mg,Mn)(CO 3 ) 2 . Another
example of a white iron ore is siderite, FeCO 3 .
A dissertation on zinc ores was defended by Geijer in 1779 [9]. It contains a
historical introduction, as did many of Bergman’s works (according to Partington,
Bergman often relied on Pott as a source of historical information [10]), followed
by analysis and discussion of different types of zinc ores. In a 1782 dissertation on
lithomerge, a kaolinite clay mineral, Bergman found a method of selectively precipitating aluminium carbonate with magnesium carbonate from a solution of the
clay in sulphuric acid [11]. This method of separating different kinds of earths also
came to good use in a dissertation on asbestos defended the same year (Sect. 11.4).
Bergman and his student Robsahm analysed 13 different varieties of asbestos [12],
which were found to be composed of lime, magnesia, clay, silica and calx of iron,
i.e. oxides of calcium, magnesium, aluminium, silicon and iron.
2 From a letter to
Bergman from Scheele, dated in May 1782, it is clear that Bergman had asked
Scheele to analyse asbestos, but that Scheele had found no time to do so.
2
Asbestos is a heterogeneous group of fibrous minerals. They are all silicates of elements like
calcium, magnesium and iron.
25.3 Mineralogial Remarks
345