ANNALS

OF

PHILOSOPHY.

DECEMBER, 1817.

ARTICLE I.

Biographical Account of William Brownrigg, M.D. F.R.S. By Joshua Dixon, M.D.

(Concluded from p. 338.)

IN four lemmas, introductory to his account of the improvements proposed in the art of preparing white salt, Dr. Brownrigg shows, by indisputable facts and arguments, that white salt obtained by the usual methods is inadequate to the purposes to which it should be applied; that it is not calculated for the preservation of provisions; and that it assists, rather than prevents, putrefaction. The dissipation of the volatile acid in large quantities, in consequence of the violent heat used in the process; the mixture of calcareous and ferruginous earths, of heterogeneous salts, of sulphureous substances, and of impurities occasioned by the several additions to white salt; appear, from accurate experiments, the sole cause to which its evident defects can be ascribed. As a remedy for these defects, Dr. Brownrigg proposes two methods of obtaining salt superior in strength and purity to every other kind: first, by a more complete impregnation of it with its acid; and, secondly, by a more perfect separation of its impurities. According to the plan which he suggests, a kind of white salt may be prepared, either from sea water, natural brine, or rock salt dissolved in weak brine, or sea water. The construction of the salt marsh should correspond to that adopted in France, and the size of the boiler should be the same as what is used by the Dutch; the clarification of the brine is to be effected by the mixture of whites of eggs, and the alkaline VOL. X. N° VI. 2 C

salt of the brine to be neutralized by the addition of a proper quantity of sour whey. The violent boiling which he recommends in this part of the process cannot occasion any considerable dissipation of the acid, as experiments discover that no portion of it is separated until one-third of the water is exhaled. The salt thus prepared, though sufficiently adapted to culinary purposes, may yet further be improved by the following expedients. By the addition of such a quantity of pure spring water as may be sufficient to dissolve the salt and produce a strong brine, a sediment will be deposited at the bottom of the vessel. A slow evaporation of this clear solution of white salt must then be promoted by a gentle, equal, and regular heat; and, on the first appearance of crystallization, such a proportion of muriatic acid must be mixed with the salt as may prevent the ascendancy of either the acid or alkali. The salt remaining after the evaporation is completed will surpass in purity, strength, and efficacy, every other preparation. Though the expenses attending this process can only be ascertained and determined by proper experiments; yet, from Dr. Brownrigg's calculations, it is probable that the price of this refined salt would be less than that of common bay salt, and would not exceed that of common white salt. He concludes this ingenious and elaborate publication by recommending the interference of the Legislature in directing a more comprehensive inquiry into the practicability of the improvements proposed; in erecting salt-works for the purpose of making additional and more accurate experiments; in appointing skilful and judicious persons to the inspection and superintendance of them; and in regulating the price and quality of salt by one common and established standard.

The superior advantages of the processes which have been explained over that of Mr. Lowndes must be sufficiently obvious, inasmuch as the latter is confined entirely to boiled brine salt, whilst Dr. Brownrigg suggests improved methods of obtaining both bay and white salt. Mr. Lowndes's process, likewise, can neither be admitted as perfect and unexceptionable, nor, with justice, can it be considered as his exclusive discovery. The addition of the alum, which constitutes its chief peculiarity, had long before been practised in Cheshire; and, in all probability, the uniform and moderate heat used in the preparation of the salt was solely instrumental in producing those effects which were improperly attributed to the alum.

This work was so highly approved by the Royal Society, that they conferred upon Dr. Brownrigg the singular honour of directing an abridgment of it to be made by Mr. William Watson, a most worthy member of that establishment, which they published in the 46th volume of their Transactions. His improvements in the saltpans and furnaces have been adopted in the Cheshire and Droitwich salterns, and in many other parts of the kingdom. In consequence, a stronger and purer boiled salt than that which was formerly made is now prepared at all the British salt-works, and the demand for

their salt was greatly increased, especially before the North Ameri

can war.

To this judicious and valuable publication the late celebrated Professor of Chemistry in the University of Edinburgh, Dr. Joseph Black, when explaining in his lectures the art of preparing and preserving common salt, always made a particular reference, respectfully intimating that the ample instructions there given superseded the necessity of expatiating on the subject. Subsequent writers, also, who have pursued the same track of inquiry, whilst they unanimously acknowledge their obligations to Dr. Brownrigg, mention his labours in terms of praise which reflect equal honour on his talents and their own judgment.*

The metal platina di pinto, juan blanco, or white gold, was the next object of Dr. Brownrigg's attention. The first specimens of this article, having been originally carried from Carthagena, in New Spain, to Jamaica, were brought to England in 1741, by Mr. Charles Wood, a skilful and inquisitive metallurgist. They were given by him to his relation Dr. Brownrigg, who presented them to the Royal Society in 1750, accompanied with an accurate and ingenious account of its origin and properties, which was inserted in the 46th volume of their Philosophical Transactions, under the title of Several Papers concerning a new Semimetal† called Platina. The specimens were, first, those of its ore in a natural state; secondly, when purified; thirdly, when fused; and, lastly, as forming part of the pummel of a sword.

Don Antonio d'Ulloa, a Spanish mathematician, had in the year 1748 slightly mentioned this intractable metallic stone, as he improperly terms it; which is represented as preventing the separation of gold from its ore. Dr. Brownrigg, however, is entitled to the credit of having communicated to the public the earliest scientific information respecting it. He introduces the subject with observing that naturalists yet remain unacquainted with a great variety of mineral substances; and that, of those already discovered, there are many species whose properties are imperfectly known. comparing the specific gravity of gold with that of mercury and platina, he notices the singular qualities of the latter, and proves from them that it is in many respects an exception to certain axioms admitted in metallurgy. Platina, he observes, is not found in the form of a pure ore, but in the state of dust or grains, blended with ferruginous impurities, which are easily attracted and separated by the magnet. He next mentions the manner of obtaining it, its

After

* Dr. Campbell, in his Political Survey of Great Britain, noticing Dr. Brownrigg's treatise upon salt, calls it "a very learned, ingenious, and solid performance; than which," he adds, "there is not perhaps any thing more concise or more correct in any language." This eulogium from the pen of one who was as well qualified to form a proper estimate of merit as he was incapable of conferring undeserved praise, is not less flattering than it is just.

+ Platina has been improperly stiled a semimetal: for, when all extraneous substances are removed, it possesses the distinguishing qualities of a metal, viz. malleability and fixity.

abundance in the Spanish West Indies, the method of fusing it, and the difficulty of effecting the process even by saline additions. From its being specifically heavier than other metals, and from its ready combination with them, arose the practice among the Spaniards of adulterating gold with it; in consequence of which the mines were closed, and the metal became much scarcer. The inference which Dr. Brownrigg draws from his experiments and researches is, that platina has a great affinity to gold in its qualities of fixedness and solidity, to which in other respects it is nearly allied. He concludes with intimating that, similar to many metallic substances, it may probably be possessed of several wonderful properties, and may on some occasions be productive of very important advantages to mankind. Mr. Wood had, with great accuracy and sagacity, previously subjected this metal to various experiments, which Dr. Brownrigg purposed to repeat, intending at the same time to make further experiments upon it with sulphureous and other cements, as also with mercury, and many corrosive menstrua. In performing these experiments, he remarked that platina does not wholly resist the action of lead in cupellation, as he had before supposed.

The extraordinary nature of this newly-discovered metal has long excited the curiosity and attention of philosophers; but the prohibition of its sale has hitherto prevented its application to practical uses. It is, however, to be hoped that regard to their own interests, if not to the improvement of the arts and sciences, will no longer suffer the Spaniards to continue the interdiction of this valuable article. Their apprehensions lest it should be employed in the adulteration of gold are now groundless, since the fraud may, without difficulty, be detected by the methods which chemists have proposed. When we consider that in this metal the fixity of gold is joined to the hardness of iron, that it cannot be acted upon by acids, that it is not injured by water or air, and that it is incapable of being corroded and impaired by rust, we are led to indulge the sanguine expectation that, if its commerce was subject to no restrictions, benefits would result to society of which we can at present form only an imperfect conception. Mankind will then pay a just tribute of gratitude and veneration to the memory of that person who gave to the world the first intelligence of its existence and properties. Long were the miners of Peru acquainted with this metal before its introduction into Europe; and if Dr. Brownrigg had not brought it forward to public notice, the knowledge of it might, even in the present age, have been confined to that illiterate class of men.

In some explanatory notes to A descriptive Poem addressed to two Ladies at their Return from viewing the Mines near Whitehaven, published in 1755 by John Dalton, D.D. is contained a

*

* This poem, and its explanatory notes, are inserted in Pearch's Oxford Collec tion of Poems.

short account of those mines, which proceeded from the pen of Dr. Brownrigg. These notes are not intended to form a history of collieries, or a philosophical treatise upon their peculiar exhalations; but merely to illustrate and confirm the poet's description of the operations and appearances in the mines. An accurate relation is given of the various expedients which attentive observation and melancholy experience have at different periods suggested for the purpose of preventing the explosions of the fire-damp, and the fatal effects of the choak-damp. The scenes exhibited in those subterraneous regions, which fill the mind with awe, surprise, and terror, are delineated with equal elegance and perspicuity. The circumstances which are mentioned relative to the strata of coal, the depth of the mines, the uses of the steam-engine, the original establishment of the collieries, and their influence on the prosperity of Whitehaven, are curious in themselves, and must to many persons, from their local residence, be particularly interesting.

These notes are deserving of praise, as being a valuable specimen of topography, and as containing a faithful description of mines, the most extraordinary of any hitherto discovered, and concerning which no authentic information had appeared before the public. An indubitable proof of their merit is, that those writers who have noticed the coal-works at Whitehaven are, in a great measure, indebted for their accounts of them to Dr. Brownrigg.

In the 49th volume of the Philosophical Transactions, for the year 1756, is inserted a paper written by Dr. Brownrigg, which is intituled, Thoughts on the Rev. Dr. Hales's new Method of Distillation by the united Force of Air and Fire. The following circumstance gave occasion to this publication. Dr. Hales, who has enriched philosophy by many ingenious and valuable discoveries, had proposed a new method of distillation, by which, from the combined power of air and heat, a greater quantity of steam was raised than by any former process. The perfect separation of fresh water, in a large proportion, from sea water, was the immediate advantage which he expected from this discovery; and the benefit of navigators was his particular object. Desirous, however, of rendering its uses more extensive and important, he requested Dr. Brownrigg to consider its application to the improvement of those mechanical operations which depend on the action of steam, Brownrigg, in compliance with his friend's solicitation, carefully and attentively examined whether this discovery was adapted to increase the power and facilitate the motion of the steam-engine. Convinced that Dr. Hales's method of exciting so violent an agitation of the water was inapplicable to that machine, and prompted by the interesting nature of the subject to extend his inquiries, he considered what other expedients, unaccompanied with similar inconveniences, were calculated to produce the same effects. The improvements which he suggests in the construction and operations of the steam-engine were the result of this investigation. Although the Doctor, with that modesty which is the inseparable attendant,

Dr.