300th Birthday: Axel Fredrik Cronstedt

Axel Fredrik Cronstedt was born on December 23, 1722, at Ströpsta, an estate near Stockholm, Sweden. He was a chemist and mineralogist and is often considered one of the founders of modern mineralogy. Cronstedt is well known for the discovery of nickel in 1751, but he also discovered scheelite, coined the term zeolite, systematically studied many minerals using chemical analysis, and proposed that they should be classified by their chemical composition.

Life

Cronstedt studied chemistry, metallurgy, and pharmacy at the University of Uppsala, Sweden, starting in 1738. He never obtained a degree. In 1742, he joined the Bureau of Mines as a civil servant. However, soon after this, his father was called to perform military duty as an inspector of fortifications and required Axel’s services as an assistant. During his travels with his father, Axel saw a mine in operation for the first time. He returned to the Bureau of Mines and began to study mining and minerals and visit Swedish mining districts.

From 1746 to 1748, Cronstedt was taught how to perform chemical analyses of minerals by Georg Brandt, the discoverer of cobalt who worked at the Laboratorium Chemicum, the royal mining laboratory in Stockholm, Sweden. Cronstedt also visited the historic copper mines at Riddarhyttan, Sweden, where Brandt had discovered cobalt. Eventually, Cronstedt was appointed Superintendent of mining operations for the Swedish mining districts of Öster- and Västerbergslagen. He kept traveling, collected minerals, and performed experiments. In 1753, Cronstedt was elected a Member of the Royal Swedish Academy of Sciences. Axel Fredrik Cronstedt died on August 19, 1765, at the estate of Nisshytte, near Riddarhyttan.

Blowpipes and Minerals

Cronstedt pioneered the use of blowpipes for the analysis of minerals. Originally, blowpipes were tools used by, e.g., jewelers or glassblowers. They use a stream of air (or oxygen) that is directed through a flame. This improves the mixing of the fuel with oxygen and creates a very hot flame.

Cronstedt used a blowpipe for the discrimination of minerals. It can be used, e.g., to treat samples with a reducing flame or an oxidizing flame, and the researcher can observe color changes, melting, decomposition, or reactions with borax. These observations allowed Cronstedt to identify minerals rapidly and accurately. Based on this work, the chemist John Joseph Griffin called Cronstedt “the first person of eminence who used the blowpipe” and “the founder of mineralogy” in A Practical Treatise on the Use of the Blowpipe in 1827 [1].

Cronstedt discovered the mineral now known as scheelite (CaWO₄) in 1751. Due to its unusual specific weight, the mineral was originally named tungsten, meaning “heavy stone” in Swedish. Carl Wilhelm Scheele later prepared tungstic acid from this mineral, which ultimately led to the discovery of tungsten as an element. The mineral was renamed scheelite in his honor.

Nickel and Zeolites

Cronstedt also studied ores from the cobalt mines of Los, Sweden. He collected samples and found one that dissolved in nitric acid to generate a green solution. Miners in Germany had previously observed that there is an ore that resembles a copper ore and that dissolves in nitric acid to produce greenish solutions. However, no copper could be extracted from the ore, and the miners blamed a mischievous sprite for this trouble. They called this “cursed” ore Kupfernickel from the German words for copper (“Kupfer”) and mountain ghosts (“Nickel”). Today, we know this mineral as nickeline or niccolite. It consists primarily of nickel arsenide (NiAs).

Cronstedt observed that the mineral weathered to produce a green substance (now known to be nickel arsenate), which he heated with charcoal. He obtained a previously unknown metal and named it nickel. He presented his results in two papers published in the Transactions of the Royal Swedish Academy of Sciences in 1751 and 1754 [2,3].

In 1756, Cronstedt coined the term zeolite after heating the mineral stilbite with a blowpipe flame and observing a release of steam, or “boiling”. This effect stems from water trapped in the mineral that is released upon heating. He called the material zeolite, Greek for “boiling stone” [4].

Cronstedt’s book Försök til mineralogie, eller mineral-rikets upställning (“An attempt at mineralogy or arrangement of the Mineral Kingdom”), published in 1758 [5], was originally published anonymously because Cronstedt feared negative reactions. In this work, he proposed that the mineral kingdom should be organized on the basis of chemical analysis. The ideas were readily accepted and translations that were published later name Cronstedt as the author.

Axel Fredrik Cronstedt is the answer to Guess the Chemist (132).