SCI-TECH & AGRI

From medicine to metallurgy - William Wollatson (1766 - 1828)

WILLIAM WOLLASTON was a contemporary of Martin Klaproth (The Hindu, October 31, 2002). He was born at Dareham, England, in a family reputed for its interests in science and theology.

On completing his school education, in 1782 he entered Caius College, as a medical student. But he pursued the study of botany, astronomy and chemistry. His interest in chemistry was stimulated by his classmate Smilthson Tenant.

Wollaston graduated from Cambridge University in 1787. He then completed his M.D. (1792) at London. In 1802, he decided to abandon the medical profession, and to devote all his time for research in science, living on moderate means.

For this purpose, he built a private laboratory behind his house near London.

He practised the art of small-scale chemistry. When the renowned Swedish chemist Berzelius (1779-1846) visited his laboratory, he was astonished to see that the whole of Wollaston's chemical apparatus consisted of a few bottles of common reagents: these were so stoppered that their contents could be extracted only in drops. Substances were investigated on small glass plates.

Wollaston formed a partnership with his friend Tenant, who bought a large quantity of crude platinum ore, which lay idle. This continued to resist the efforts of chemists for producing platinum in a malleable state.

Wollaston dissolved the ore in aqua regia and precipitated a complex salt by means of ammonium chloride, to which he added bars of iron. He treated the precipitate with aqua regia and ammonium chloride. He repeated the operations a second time to yield a precipitate with unexpected properties. When it was treated with nitric acid, it gave an amalgam; the latter on being treated with mercury and decomposed by heat, left a white metal, which he called `palladium' (after Pallas, an asteroid).

It was Wollaston's skill in working with small quantities that resulted in his discovery of the new metals (July 1802). From one thousand grains of crude ore, he had extracted five grains of palladium and four grains of rhodium.

Wollaston made further refinements to his method — slow thermal decomposition of the ammonium salt, avoidance of burnishing, sieving and sedimentation. This process produced a uniform powder, from which Wollaston made malleable platinum by compressing, heating and hammering.

His process was not immediately adopted in industry. Today it is recognised as a standard technique in modern powder metallurgy. Wollaston proved himself a versatile scientist, working in varied fields:

Crystallography, optics where he invented the reflective goniometer and presented experimental support for Hygens wave theory and physiology.

He received honours like the Copley Medal for publishing over 50 papers; firstly Secretary (1802) and later President of the Royal Society (1820).

He made useful articles for industry from his malleable platinum: wires, crucibles and vessels for storing concentrated sulphuric acid. He made 30,000 pounds that justified his earlier decision to abandon medicine.He revealed the details of his process in an elaborate Bakerian lecture to the Royal Society shortly before his death (December 22, 1828). (The Dictionary of Scientific Biography Vol. XIV).

R.Parthasarathy

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