Page:Cyclopaedia, Chambers - Supplement, Volume 1.djvu/931

 I N K

A proof that the acids of the vitriol leave the particles of the iron in the pores of the molecule of the galls fufpended in the infufion, and that to this reviving or the iron alone is owing the biack colour of the liquor, is this; that it alter the Ink is thus made a little frefh acid or ip.nt or vitriol be added, the particles or iron immediately receive it, which could not be, if the acid th'ey had before poneiied were not taken from them. The confequence ut their receiving th.s new acid is their being again dtllolved and reduced to the form of vitriol, fo that their revivincation is del troy eu j and as this alone occalioned the black colour of the Ink, this I alfo difappears, and the liquor becomes limpid and clear; | vitriol in the ftate of vitriol not being able to mate a foiu- \ tion of galls black, nor that folution to turn vitriol into iron a fecond time, when it has already abforocd as much or tae acid which reduced it to that lbate as it could. It is on this principle that verjuice, lemon-juice, and other vegetable acids take out ftains ol Ink from hnnen; thole ltains depending on the effect of plain iron, and theie acids converting that iron into vitriol again.

It is plain from what has been advanced, that galls aft as abforbents in the making Ink with vitriol; nor is this the only inftance in which they are able to aft in the lame manner; for they fupply the place of the common abfor- bents, fuch as fait of tartar, lime-water, fpirit of lal ammo- niac, and the like, in precipitating metallic iblutions. go alfo are all the other vegetable intufions which will make Ink with vitriol; but as galls make a better Ink than any other of the vegetable infulions, fo they alio adt much more powerfully than any other in the precipitating metals from their folutions.

It might be expected, that as galls aft in the metalline folutions like fait of tartar, lime-water, and the ike, fait of tartar and thofe other fubftances fhould adt like galls in a folution of vitriol, and turn it into Ink, but the difference is, that while thefe adt as mere abforbents, and only take up the particles of acids in the vitriol, the galls adt as abfor- bents and fulphureous bodies at once, taking up the acid particles and carrying them out of the ferrugineous ones, and by this means decompounding the vitriol, and leaving the iron of it revived and in the ftate of iron. Mem. Acad, Par. 1707.

Any abforbent or alkali, loaded with fulphureous particles, will make Ink with a folution of vitriol in the manner of the infufion of galls, tho* no limple abforbent can. Thus the fcoriae of the regulus of antimony, without iron, diflblved in a large quantity of water, give a liquor charged at once with an alkali, and with the fulphur of antimony; and this liquor makes Ink, with a folution of vitriol, as well as galls. In the fame manner hot water poured upon quicJc-lime and orpiment, after {landing five cr fix hours, becomes a lime- water highly impregnated with the fulphur ol the orpiment; and this being like the other, at once an abforbent and a fulphureous body, afts like the former in the manner of galls, and turns a folution of vitriol into Ink. The nature of iron alfo confirms thefe opinions; we know it to be a very ful- phureous metal, and thence very ready to receive acids; and it is eafy to conceive, that when it has once received them, and is converted into vitriol, nothing can diveft it of them perfectly, and reftore it to the ftate of iron again, but a liquor equally fulphureous, and equally ready to receive them.

Tho' many vegetable fubftances are able to fupply the place of galls in the making of Ink with a folution oi vitriol, yet all are not fo; and the reafon why the galls do it better than all the others that are fo, is, that they are the greateft and molt powerful of all the vegetable abforbents. The galls have alfo a glutinous property, which renders an infu- fion of them capable of fultaining the revived particles of iron. This is wanting in many of the other vegetables ufed on this occafion; and fuch tho' they immediately make Ink with a folution of vitriol by reviving the particles of iron, yet not being able to fuftain them when revived, they foon after fink to the bottom, and the liquor becomes clear and limpid over them. A little gum arabic, or any thing of the like nature, added to the mixture, remedies this fault by giving them the glutinous quality of the galls; and after this the iron no more fublides, and the Ink remains good. All vegetables are more or lefs proper to make Ink with a folution of vitriol, as they more or lefs approach to the na- ture of the galls, and are abforbent and agglutinating. Of! . all the vegetable fubftances, none appear To good for the j making Ink as that clafs of aftringents, which aft by thicken- ing the humors, ftrengthening the parts, and deitroying the ■ acids which irritate them. Of this kind are the cortex gra- 1 natorum, balauitines, fumach, red rofes, acorns, and the : leaves and wood of the oak; and finally, the galls. The ' virtues of all thefe fubftances in medicine depend wholly upon their being abforbents and fulphureous bodies, as the . galls have been proved to be. The purging remedies on the other hand, produce no iimilar effect. Infufions of fena, j agaric, jalap, colocynth, tobacco, and white and black hel- lebore, have all been feverally tried in mixture with a folu- tion pf vitriol, and not one of them, give the liquor any

INK

blacknefs, nor feem to have any tendency toward it. This confirms what lias been already oblerved; for thefe purging medicines have no abforbent quality, but, on the contrary, they all contain active and pungent ialts, on which their pur- gative virtue depends. Mem Acad. ."ar. 1707. On the other hand, rhubarb and fnj robalaiu which Have an aftringent virtue, which they exert after their purging, mult cunfequently contain fome abforbent and agglutinating par- ticles, and accordingly infulions of thefe turn the Iblutions of vitriol into Ink.

Thefe experiments are not limited in their ufe to the making of Ink alone, nut may be extended much farther j tor if, as it appears very certain, no vitriol can make Ink, but fuch as contains iron; and no vegetable can make Ink with that vi- triol, butfuchaspollcfi.es an aftringent virtue j thefe twu fubftances become telts to one another, and may ferve to find out the virtues of unknown fuuitances. For inftance, any unknown vegetable may be tried by its -infufion in mixture with a folution of vitriol j if it make it black, it will be ktiowh to be an aftringent j if not, otherwifei And in any vitriol the telt may be eanly made whether it contains iron; fince it it does, it will become biack 111 folution with ''alls; if otherwde, it will not. All the vitriols of copper, or the common blue kind, and the reft, having no power of chang- ing an inrunon of galls into Ink. Mixtures or bine and green vitriol make a reddiih Ink; and probably all thole native vi- triols which make an Ink of the fame reddiih colour, con- tain a quantity of copper, which is the bafts of blue vitriol, mixed with their iron. Sy/npathetie Inks. Every fort of liquor with which a perfon may write fo that the letters do not appear till there is finite particular means ufed to give them a colour different from that of the paper, are called by the name of lymtaihetic Inh j and of thefe there are a great many kinds oelcnbed in the writings of Baptifta Porta, Lemery, and other authors. All thefe Inks may be regularly diitributed into different clafles, according to the different means which are to be ufed to make them appear; and thefe are in general the four following : 1. By giving a new liquor or the vapour of a new liquor a place on the paper, on which the letters are written with the naturally mvihble Ink. 2. By expofing the paper to the air, by which mea..s the letters at firit invillble will appear. 3. By palling gendy over the letters a matter of fome remarkable colour reduced to a fine powder. And 4. By expofing the paper to the fire.

This hit is by much the belt method, and is fo general, that it may be prudently ufed to all papers fulpected or containing any fecrct writing, as it feldom fads to difepvef it. AH the common Inks of this kind however, when they have been once made to appear, either by lire or by any other method, can never be made to disappear again; but there is one kind defcribed by Mr. Heliot, in the Memoirs of the Aca- demy of Sciences of Paris, and fmce tried many times with us, and eilewhere, which, tho' the letters it gives are in them- felves invifible, and appear like thofe of fome other of thefe Inks, on their being held to the fire, yet they after that will fade and difappear on the paper again, and may be re-pro- duced in this manner feveral times. This therefore is the firft known Ink of a fifth general clafs, of which future re- fearches may difcover perhaps more.

Of the firft clafs of fympathetic Inks, of thofe which do not appear till the paper on which they are written be made to imbibe another liquor, or the vapour of another liquor, are the following kinds :

1. Mr. Lemery's orpiment kind. This is compofed of dif- ferent liquors; the letters are to be written with a folution of lead or litharge in diftilled vinegar. This being dried in the air, not at the fire, does not appear at all upon the paper; if this be rubbed over with a pencil dipped in a folu- tion of orpiment in lime-water, or if the paper be only made to receive the vapour of that water, the letters im- mediately appear and are at firft yellow, and afterwards be- come black. Thefe may be made to difappear again, if the paper be rubbed over with an acid liquor, fuch as aqua fortis or fpirit of nitre, and may be again made to appear, if be- fore the paper be dried a folution of orpiment be again rub- bed over them. It is eafy to perceive, that all thefe effedls are produced by fucceeding folutions and precipitations.

2. The golden fympathetic Ink. This is made by diffolving in aqua regia as much gold as that menftruum can take up, and then adding to the liquor five or fix times as much wa- ter; in another veffel there muft be fome tin diifolved in aqua regia, and when that menftruum has alfo taken up as much of the metal as it can, there is to be added to it an equal quantity of common water. The letters mult be written on white paper with the folution of gold, and the writing being dried in the fhade the letters will not appear, at Ieaft not for feven or eight hours afterwards; dip a pen- cil in the folution of tin, and rub that over the folution of gold with which the letters were written, and they will ap- pear of a beautiful purple.

It might be fuppofed, that any other metals which were foluble in the fame acid menftruum would equally produce this effect •, but experiment fhews, that this is not the cafe,

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