Percival Norton Johnson died on the 1st of June, 1866, aged 73. He was the only son of John Johnson, at one time the only commercial assayer in London; and after working with his father for some years, he established himself in Hatton Garden half a century ago.
He rapidly rose to the highest eminence as an assayer and metallurgist; and his opinion was so much sought after that he could hardly get through the work which crowded upon him.
It is not a little remarkable that the extreme accuracy of his assays was made a ground of objection to them. He for the first time reported the exact amount of gold and silver in the specimens submitted, whereas, before, the quantities had only been stated approximately; and this was not relished by the buyers of bullion, inasmuch as contingent advantages in buying upon exactly known value were not so great. Upon this being represented to him by the merchants, he at once stated that he was willing, if required, to purchase all bars upon his own assays ; and this was the reason of his taking up the refining business, in which he so largely and successfully engaged. His ability in this (as in all other branches that he entered upon) was soon recognized publicly; and when the gold bars from the Brazilian " Gongo Soco" mines, which came over in very large quantities, were refused at the Mint on account of brittleness, he was consulted on the matter, and undertook to refine and toughen them, in which he perfectly succeeded.
It was in this gold that he discovered the existence of palladium; and having succeeded in its separation, he introduced it commercially, at once determining and making known the best uses to which it could be applied.
After he had been in business some years he visited Germany, and was much interested in mining operations there, to which he gave special attention. It was at this time that he met with the compound alloy called "German silver," then in a very crude state of manufacture. He brought over with him some of the metal, analyzed it, and upon the basis of his analysis he commenced and carried on its manufacture, and introduced it to general use, laying the foundation of the enormous business which has since arisen in this branch of metallurgy.
About this time he was much engaged in mining pursuits, and was consulted upon, and visited professionally, nearly all the mines in England, Wales, Scotland, and Ireland, and many important ones abroad. He was the first to introduce into Cornwall the German shaking-, jigging-, and washing-table, with important improvements of his own. He will always be remembered throughout the mining districts for his great kindness and consideration toward the miners, whose social condition it was his constant aim to improve. At great expense to himself, he erected schools in the neighbourhood of the mines, and took an active part in their supervision. He also used his utmost endeavours to alleviate the toil of the workmen in ascending and descending mines, and with this view he, at the Tamar mines, made the experiment of a sloping gallery, which ran for a considerable distance under the river, by which means the miners could walk up and down without the use of a ladder.
Amongst his many inventions of less note may be mentioned several pottery colours, amongst them the "rose-pink," at a time when that colour was much wanted in the potteries.
His greatest success, however, and that which has proved the most valuable to the progress of chemistry and manufacture generally, was the platinum business. To him undoubtedly belongs the credit of having been the first who successfully refined and manufactured platinum upon a commercial scale, and introduced it for the important purposes to which it is specially adapted. The first large and perfect sheet of pure platinum ever produced was made by Mr. Johnson at 79 Hatton Garden; and, seeing the immense importance of the metal, he ever since made it his speciality.
His eminence as an analyst should also be noticed; so great was it, that the only other commercial assayers in London, though his rivals, used to send him all compounds or minerals of a difficult and complicated nature to report upon for them.
Accomplished as he was in his department, and singularly successful in perfecting whatever he undertook, his opinion was always sought for with earnestness and received with confidence. Few men have worked more perseveringly and effectively for the improvement of their profession.
Mr. Johnson was elected a Fellow of the Royal Society on April 30, 1846.
Source: Proceedings - Royal Society of London - Volume 16 - 1868