A History of Inventions and Discoveries: Sympathetic ink.

A History of Inventions and Discoveries.
By John Beckmann,
Public professor of economy in the University of Gottingen.
Translated from the German, by William Johnston.
Third edition, carefully corrected, enlarged by the addition of several new articles.
In four volumes.
Vol. 1.
Printed for Longman, Hurst, Rees, Orme, and Brown; Baldwin, Cradock, and Joy; R. Priestley; R. Scholey; T. Hamilton; W. Otridge; J. Walker; R. Fenner; J. Bell; J. Booker; E. Edwards; and J. Harding.

* Tuta quoque est, fallitque oculos, e lacte recenti/ Litera: carbonis pulvere tange; leges. De arte amandii, lib. iii. v. 629.
*2 Lacte incide notas; arescens charta tenebit/ Semper inadspicuas; prodentur scripta favillis. Ausonii Epist. zziii. v. 21. The poet afterwards teaches other methods of secret writing. Eneas, in Poliocreticis, cap. 31. and Gellius, lib. xvii. cap. 9. mention the like.
*3 Colum. de re rust. x. 354. and xi. 3, 60. p. 773.
*4 Tithymalum nostri herbam lactariam vocant, alii lactucam caprinam: narrantque lacte ejus insripto corpore, cum inaruerit, si cinis inspegatur, apparere litteras; et ita quidam adulteras allequi maluere quam codicillis. Plin. lib. xxvi. cap. 8. p. 400.
If we give this name to any fluid which, being wrote with, the letters, under certain circumstances, or after a certain operation, will become conspicuous and legible, such liquids were known in very early periods. Among the methods which Ovid teaches young women to deceive their guardians, when they write to their lovers,* he mentions that of writing with new milk, and of making the writing legible by coal-dust or soot. Ausonius proposes the same means to Paulinus; *2 but his commentators seem not to have fully understood his meaning; for favilla is not to be explained by favilla non modice calida, as Vinetus has explained it, but by fuligo. That word is often employed by the poets in the same sense. As a proof of it, Columella, speaking of the method, not altogether ineffectual, and even still used, of preserving plants from insects by soot, calls it nigra favilla; and afterwards, when mentioning the same method, free from poetical fetters, he says fuliginem quæ supra focos tectis inhæret.*3 It may be easily perceived, that instead of milk, any other colourless and glutinous juice might be employed, as it would equally hold fast the black powder strewed over it. Pliny, therefore, recommends the milky sap of certain plants for the like purpose. *4

There are several metallic solutions perfectly colourless, or, at least, without any strong tint, which being used for writing, the letters will not appear until the paper be washed over with another colourless solution, or exposed to the vapour of it; but among all these there is none which excites more astonishment, or from which naturalists can draw more conclusions, than that which consists of a solution of lead in vegetable acid, and which by the vapour of arsenical liver of sulphur becomes black, even at a considerable distance. This ink, which may be employed by conjurers, proves the subtlety of vapour, and the porosity of bodies; as the change or colouring takes place, even when the writing is placed on the other side of a thin wall.

This effect presented itself perhaps accidentally to some chemist; but the discovery is not of great antiquity. Wecker, who compiledry is as follows: his book de secretis from Porta, Cardan, and several old writers, and printed it for the first time in 1582, and gave a third edition in 1592, must have been unacquainted with it; else he certainly would not have omitted it in the fourteenth book, where he mentions all the methods of secret writing. Neither would it have been unnoticed by Caneparius, whose book de atramentis was printed at Venica, for the first time, in 119, in quarto.

* The sixth observation of the second century is as follows: Magnetic waters which act at a distance. An astonishing effect, indeed, is produced by the contest of the following waters, which are thus made. Let quick-lime be quenched in common water, and while quenching, let some orpiment be added to it (this, however, ought to be done by placing warm ashes under it for a whole day), and let the liquor be filtered, and preserved in a glass bottle well corked. Then boil litharge of gold well pounded, for half an hour with vinegar, in a brass vessel, and filter the whole through paper, and preserve it also in a bottle closely corked. If you write any thing with this last water, with a clean pen, the writing will be invisible when dry; but if it be washed over with the first water it will become instantly black. In this, however, there is nothing astonishing; but this is wonderful, that though sheets of paper without number, and even a board be placed between the invisible writing and the second liquid, it will have the same effect, and turn the writing black, penetrating the wood and paper without leaving any traces of action, which is certainly surprising; but a fetid smell, occasioned by the mutual action of the liquids, deters many from making the experiment. I am, however, of opinion, that I could improve this secret by a more refined chemical preparation, so as that it should perform its effect through a wall. This secret I received, in exchange for others, from J. Brosson, a learned and ingenious apothecary of Montpelier.
*2 Tachenii Hippocraticæ medicinæ clavis, p. 236. This work was printed in 1669, viz. at Venice and Francfort.
*3 Collectanea Chymica Leydensis, id est, Mætsiana, Margaviana, Le Mortiana - - - edidit Christ. Love. Morley. Lugd. Bat. 1684, 4to. p.97.
*4 For an account of various kinds of secret writing see Halle, Magic oder Zauberkrafte der natur. Berlin 1783, 8vo. v. i. p. 138.
*5 The works which treat of this ink may be seen in Weigerl's Chemie, p. 284.
The first person who, as far as I have been able to learn, gave a receipt for preparing this ink, was Peter Borel, in Historiarum et observationum medico-physic, centuriæ quator. In this work, which was printed, for the first time, in 1653, and a second time in 1657, at Paris, and of which there were several editions afterwards, the author calls it a magnetic water, which acts at a distance.* After the occult qualities of the schoolmen were exploded, it was customary to ascribe phænomena the causes of which were unknown, and particularly those the causes of which seemed to operate without any visible agency, to magnetic effluvia; as the turmalin was at first considered to be a kind of magnet. Others concealed their ignorance under what they called sympathy, and in latter times attraction and electricity have been employed for the like purpose. Borel, who made it his business to collect new observations that were kept secret, learned the method of preparing this magnetic water from an ingenious apothecary of Montpelier, and in return taught him some secrets. Otto Tachen, a German chemist,*2 afterwards thought of the same experiment, which he explains much better, without the assistance of magnetism or sympathy. The receipt for making these liquids, under the name of sympathetic ink, I find first given by Le Mort, in the Collectanea chymica Leydensia,*3 and that name has been still retained.*4

Another remarkable kind of sympathetic ink is that prepared from cobalt, the writing of which disappears in the cold, but appears again of a beautiful green colour, as often as one chooses, after being exposed to a moderate degree of heat.*5

* Hist. et M'emoires de l' Académ. des Sciences à Paris. Année 1737, pp. 101 and 228.
*2 J. A. Gerneri Historia cadmiæ fossilis, sive cobalti, Berolini 1744, 4to. Lekmans Cadmiologia, i. 79.
*3 This account, together with Teichmeyer's receipt for preparing it, may be found in Commercium litterarium Norimbergense, 1737, p. 91.
*4 Copiosius minera bismuthi tam ab aqua forti quam ab aqua regia dissolvitur, restante pulvere albo corroso; solution in aqua forti roseum colorem sistit, quæ si sali in aqua soluto, secundum præscriptum D. J. W. in clave, affundatur, abstrahatur, ex residuo extrahitur sal roseum, quid pulverisari et cum spiritu vini extrahi potest: adeque hæc autrix jana anno 1705 publice totum processum et fundamentum sic dicti atramenti sympathetici, quod a calore viridescit, evulgavit. Pot., Observatiomum chymicarum collectio prima. Berolini 1739, p. 163.
*5 So thinks Gernes in Selecta physico-oeconomica, or Sammlung von allerhand zur naturgeschichte gehörigen begebenkeiten. Stutgard, vii. p. 22.
The invention of this ink is generally ascribed to a Frenchman, named Hellot. He was, indeed, the first person who, after trying experiments with it, made it publicly known, but he was not the inventor; and he himself acknowledges that a German artist of Stolberg first showed him a reddish salt, which, when exposed to heat, became blue, and which he assured him was made from Schneeberg cobalt, with aqua regia.* This account induced Hellot to prepare salts and ink from various minerals impregnated with cobatl; but A. Gesner proved, long after, that this ink is produced by cobalt only, and not by marcasite.*2

When Hellot's experimetns were made known in Germany, it was affirmed that professor H. F. Teichmeyer, at Jena, had prepared the same ink six years before, and shown it to his scholars, in the course of his lectures, under the name of sympathetic ink.*3 It appears, however, that it was invented, even before Teichmeyer, in the beginning of the last century, by a German lady. This is confirmed by Pot, who says that the authoress of a book printed in 1705 of D. J. W. in clave, had given a proper receipt for preparing the above mentioned red salt, and the ink produced by it.*4

I should be very glad if any one could give me information respecting this book, for I must confess, that I am not able to conjecture what kind of a work it is. If it be true that Theophrastus Paracelsus, by means of this invention, could represent a garden in winter, it must be undoubtedly older.*5

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