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A smaller volume, of 302 pages, without an index, has for title, Bibliotheca exotica, sive Catalogus officinalis librorum peregrinis linguis usualibus scriptorum; and a fourth part, forming 759 pages besides an index of the authors, is called, Bibliotheca librorum Germanicorum classica; that is, A catalogue of all the books printed in the German language till the year 1625. By the indices, and the proper arrangement of the matter, the use of this work is much facilitated. I must, however, observe that the oldest catalogues had the same faults as those of the present time, and that these have been copied by Draudius. Many books are mentioned which were never printed, and many titles, names, and dates, are given incorrectly; but Draudius, nevertheless, is well worth the attention of any one who may be inclined to employ his time and ingenuity on the history of literature; and his work certainly was of use to Haller when he composed his bibliotheca.

* I shall refer those who may be desirous of seeing a humorous comparison of the catalogues of 1619 with those of 1780, and of the state of literature at that period, with what it is at present, to Frommichen's Essay in the Teutsche Museum for September 1780, p. 176.

AURUM FULMINANS.

Ir gold be dissolved in aqua-regia, and precipitated by volatile lixivious salt, or by fixed lixivious salt, when the aqua-regia has been prepared with sal ammoniac, a yellow powder will be obtained, which, when heated, or only bruised, explodes suddenly with a prodigious report. The force of this aurum fulminans is terrible, and, in the hands of incautious persons, has often occasioned much mischief. But, however powerful, it cannot, as some have imagined, be employed instead of gunpowder, even were not this impossible on account of the high value of the metal from which it is made; for explosion does not take place when the powder is confined. Phænomena of this kind are always of importance, and afford subject of speculation to the philosopher, though no immediate use can be made of them. Experiments, however, have rendered it probable that this powder may possess some medicinal virtues, and we are assured that it can be employed in enamel painting.

He who attempts to trace out the invention of aurum fulminans is, like a person bewildered in

* An account of the principal writers who have treated of aurun fulminans may be found in Weigel's Chemie, i. p. 225. See also Lewis, Zusammenhang der künste. Zurich 1764, 8vo. i. p. 172.

a morass, in danger every moment of being lost. I allude here to the immense wilderness of the ancient alchemists, or makers of gold; to wade through which my patience, though pretty much accustomed to such labour, is not sufficiently adequate. Those who know how to appretiate their time will not sacrifice it in endeavouring to discover the meaning of books which the authors themselves did not, in part, understand, or to comprehend passages in which the writer tells us nothing, or, at any rate, nothing of importance. I have, however, made my way through this labyrinth from Spielmann to the works which are ascribed to one Basilius Valentin.*

The period when this powder was invented is as uncertain as the accounts given of its composition. It is, however, probable that the discoverer was a German Benedictine monk, who lived about the year 1413; and there is reason to think that he may have made many useful observations, of which we are yet as ignorant as of the meaning of the Egyptian hieroglyphics; for both are almost equally unintelligible, though some, who possess more imagination and credulity than judgment, think they understand and can explain them, The Egyptian hieroglyphics are indeed totally

* Spielmann, Institut. chem. p. 288. Hanc calcem Bas. Valent. inter primos clare describit.

+ See the preface of Bened. Nic. Petræus to the Works of Valentin, printed at Hamburg 1717, in octavo.

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incomprehensible, but those of Valentin only in part; for when new observations have been made respecting gold, they have been found afterwards in the works of Valentin, in a passage which no one before could understand. In this case these writings are of no more utility than the answers of the ancient oracles, which were comprehended when a knowledge of them was no longer necessary, and which misled those who supposed that they comprehended them sooner. But the account of aurum fulminans in Valentin is so uncommonly intelligible, that it almost seems he either wrote in an explicit manner without perceiving it, or that the words escaped from him contrary to his intention. As the work in which it may be found, is scarce, I shall transcribe the prescription.*

"Take a pound of aqua-regia made with sal ammoniac; that is, take a pound of good strong aquafortis, and dissolve in it four ounces of sal ammoniac, and you will thus obtain a strong aquaregia, which must be repeatedly distilled and rectified until no more feces remain at the bottom, and until it become quite clear and transparent. Take fine thin gold-leaf, in the preparation of which antimony has been used; put it into an alembic; pour aqua-regia over it; and let as much of the gold as possible be dissolved. After the

* Fr. Basilii Valentini, Benedictiner ordens, Letztes testament; von Georg Philips Nenter. Med. Doct. Strasburg 1712, 8vo. p. 223.

gold is all dissolved, add to it some oleum tartari, or sal tartari dissolved in a litte spring-water, and it will begin to effervesce. When the effervescence has ceased, pour some more oil into it; and do this so often till the dissolved gold fall to the bottom, and until no more precipitate is formed, and the aqua-regia remains pure and clear. You must then pour the aqua-regia from the gold calx, and wash it well with water eight or ten times. When the gold calx is settled, pour off the water, and dry the calx in the open air when the sun shines, but not over the fire; for as soon as this powder becomes a little heated or warm, it explodes, and does much mischief, as it is so powerful and violent, that no man can withstand it. When the powder has been thus prepared take strong distilled vinegar and pour over it; keep it continually over the fire for twenty-four hours, without stirring it, so that nothing may fall to the bottom, and it will be again deprived of its power of exploding; but take great care that no accident happen by carelessness. Pour off the vinegar, and, having washed the powder, expose it to dry."

The latter part of the receipt shows that Valentin had made experiments in order to discover how aurum fulminans might be deprived of its power of exploding, and he found that this could be done by vinegar. It appears from his writings, that he

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