Scheffer’s Two Papers

However that may be, Scheffer, undoubtedly prompted by Ulloa or Bose or possibly both, very soon produced a paper for the Academy, submitted on November 19th and read on the 28th, with the title “The White Gold or Seventh Metal, called in Spain ‘Platina del Pinto’, Little Silver of Pinto, Its Nature Described” (8). In this he records that in June 1750 he received from Rudensköld a sandy specimen containing “flat triangular scales, white as silver” that were not attracted by a magnet, that the sample had been obtained from Spain and that he understood it came from the West Indies. After removing the sandy content he was left with only forty grains of a metallic nature; these he found could be melted readily with copper, that they were not attacked by sulphuric or nitric acid but dissolved in aqua regia, while with the addition of a small amount of arsenic the material melted easily. (His choice of arsenic must surely have occurred to him from the work of his master, Georg Brandt, on this element). His conclusions were:

Finally he recommended that:

This was the first accurate examination of platinum, carried out on an extremely small quantity, but immediately afterwards, and also dated November 28th, 1751, Scheffer read a short paper to the Academy “An Addendum on the Same Metal” (9), in which he refers to another sample of material that he had received from Brandt, who had also had it from Rudensköld. In this supplementary communication he reported that the metal, unlike gold, was not precipitated from solution in aqua regia by ferrous sulphate, but that it was precipitated by alkalies and by ammonia in the form of a red powder.

Scheffer was raised to the nobility in 1756, but sadly he died three years later at the age of only forty-nine. A long appreciation of his life and work was read to the Academy of Sciences on September 17th by his younger colleague Cronstedt, in the course of which he declaimed:

Cronstedt had worked closely with Scheffer from some years and must have been well aware of the events that led up to the latter’s investigation, but Scheffer claims that he obtained his first sample from Rudensköld in June 1750. It seems likely therefore that the first intimation of the new metal came from Ulloa’s book arriving in Stockholm. As Professor Arne Fredga has pointed out, Wargentin, who became secretary of the Academy in 1749, was very active in acquiring new books on natural science for the Academy library, and the report of a quite new metal would have caused something of a sensation at that time (12).

Nothing further happened in connection with platinum in Sweden for a quarter of a century. In 1777, however, a remarkable paper was presented to the Academy by a man curiously just twenty-five years younger than Scheffer. This was the great Torbern Olof Bergman, whose early career was devoted to the study of mathematics, astronomy, geography and natural history.

Bergman’s Contribution

In 1767 Wallerius, who was the first professor of chemistry appointed in Sweden in 1750 and who had published his lectures on metallurgy, decided to take early retirement at the age of fifty-eight. There were several likely candidates with good qualifications in chemistry, but on the influence of the Crown Prince, later King Gustav III, who was chancellor of the University, the chair at Uppsala was offered to Bergman who had in fact contributed only one paper in chemistry up to that time, on the manufacture of alum.

The choice was more than fortunate and proved to be well justified. Bergman rapidly reorganised the chemistry department, acquired suitable apparatus and combined lectures with laboratory work. Many Swedish students, as well as those from other countries, attended his courses. Bergman had earlier been a follower of Linnaeus, the famous classifier of plants, and he emulated his teacher in setting out to classify minerals and chemical compounds and to systematise their nomenclature. His work on affinities and his treatise De Attractionibus Electivis are well known, but he may also be regarded as the founder of chemical analysis. In short, he was one of the greatest chemists of the eighteenth century.

In the meantime chemists in other countries had been interesting themselves in the exciting new metal platinum. The first of these was William Lewis, a physician and lecturer of Kingston upon Thames near London, who had begun his experiments in 1749 and who presented his researches to the Royal Society in two papers in 1755 and 1757 (13). In Germany work on platinum was carried out by Andreas Siegmund Marggraf in 1757 (14). Not until 1758 was the interest of French chemists aroused, and then by the appearance of an anonymous little book, “La Platine, L’Or Blanc, ou le Huitieme Metal”, published in Paris in 1758. (The arithmetic seems to have gone a little astray but no doubt the missing element was mercury.) This comprised a short preface by the author, the two letters from Watson to Bose, Scheffer’s two papers, and Lewis’s first report. It is generally understood that the author was one Morin, most probably Jean Morin, a priest and a professor of philosophy at Chartres and a corresponding member of the Academie des Sciences since 1736.

From a portrait in oils painted by Lorens Pasch the Younger in 1778 in the possession of the University of Uppsala

This publication immediately prompted P. J. Macquer and Antoine Baumé to begin an investigation on platinum, published by the Academie in the November of 1758 (15), but other French chemists, including Buffon, Guyton de Morveau and the Comte de Milly, still maintained that the ‘new metal’ was nothing but an alloy of iron and gold (16).

Bergman, some ten years after his appointment as Professor, turned his attention to platinum and presented a paper to the Swedish Academy in 1777. This was subsequently printed in Latin in 1779 in Bergman’s collected “Opuscula”, in French in 1780, and in English in 1784 (17). He began by giving his reasons for feeling that a further study of the metal was desirable:

He then proceeded to explain that since solutions of platinum were always acidic, they must first be neutralised before they could be precipitated with soda (mineral alkali). When this was done, platinum precipitated as a pale golden powder.

Bergman also obtained a precipitate of platinum by means of sal ammoniac and correctly supposed this to be a triple salt. He washed and dried this precipitate (ammonium chloroplatinate) and successfully caused it to melt, finding that the resulting globules were malleable and could be hammered out into thin sheet, but that it could then not be melted by a burning mirror. (Bergman’s platinum was undoubtedly contaminated—he reported its specific gravity as only 18.)

Platinum a Distinct Metal

The concluding part of Bergman’s paper dealt with the question of whether platinum was in fact a distinct metal:

In a final paragraph Bergman expressed his view that it was a great pity that more platinum was not available in Europe so that it could be melted in some quantity, and that in the supplies of metal that do arrive there are many impurities that must be sought for with great attention to separate them all.

Bergman’s work on classification and nomenclature has already been mentioned. He continued to make use of many of the old alchemical symbols and added new ones, including one for platinum, as illustrated here, combining the old symbols for gold and silver. He also proposed the use of the name platinum instead of the older platina in line with a number of other metals for which he had adopted the Latin ending “um”.

In 1775 Bergman paid a great tribute to his predecessor Scheffer in publishing the latter’s lectures as a text book of chemistry (18). This contained a considerable amount of comment and additional matter contributed by Bergman himself, but in his preface he gives full credit to Scheffer’s work and only Scheffer’s name appears on the title page.

Bergman’s health was never strong, and it was undermined by the vast amount of work he undertook. He died in 1784, curiously at just the same age as Scheffer, forty-nine.