1 NK
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to the fixed or fugitive nature of the feveralarticles ufed in dyeing, may be applied in generalto the ufe of the fame fubftances as inks.
Red Ink is ufually made by boiling about twoounces of Brazil wood in a pint of water fora quarter of an hour, and adding to the de-coftion the requifite quantity of gum, and abouthalf as much alum. The alum both heightensthe colour and makes it lefs fugitive. Pro-bably a little madder would make it moredurable.
Blue Ink may be made by diffufing Pruffianblue or indigo through ftrong gum-water.
Tellow Ink may be made by a folution ofgamboge in gum-water.
Moll of the common water-colour cakes dif-fufed in water, will make fufficiently goodcoloured inks for moll purpofes.
Inks Sympathetic or Secret.
Thefe are all liquids which have fcarcely anycolour in their common Hate, and thereforewhen characters are traced with them on paperthey are invifible, or nearly fo, at firft, but acolour is given to them either by applying fomechemical reagent, or by mere heat. A con-fiderable number of thefe have been invented,fome of which may be juft enumerated.
The fympathetic ink of cobalt is the beftknown and the molt Angular. Any folutionof this metal that contains muriatic acid in anyform becomes green when heated, but returnsto a ftate nearly colourlefs when cold. Thisalfo will appear and vanifh alternately by heat-ing or cooling. When the cobalt is pure thecolour approaches ftrongly to blue. See Cobalt .
Characters written with lemon-juice are in-vifible at firft, but on ftrongly heating the paper,the extractive matter of the lemons turns brown,and thus becomes vifible.
Sulphuric acid moderately diluted, anfwersin the fame way. On heating the paper thewater of the acid flies off - , the latter becomesthereby concentrated, and a£ts on the paper,making it brown.
Of the fecret inks formed by the aCtion ofreagents, the metallic folutions that are black-ened by a liquid fulphuret, or fulphuretted hy-drogen gas, are the beft known. Thefe metallicfolutions are thofe of lead, filver, bifmuth, andmercury.
The acetite of lead is one of the moll conve-nient. Letters written by any of thefe folutions,are at once blackened and rendered vifible by-being wetted with the fulphuretted folution, ormore flowly by expofure to the gas. The io-
a Emmcrling, Lenz, Kiryiran, Jamefon, Hauy, Brochant.
Tranf xcii. p. 206. * I
19 )
lutions may be very dilute, as the deepening ofcolour is very powerful.
A weak folution of gallic acid diluted to becolourlefs, will alfo be blackened by any fait ofiron.
Pruffiat of potafh will likewife become blueby any folution of iron.
IRON. Ferrum. Lat. Fer . Fr. Eifen. Germ.Jem. Dan. Jam. Swed. Mars. Alchem.
Iron is a metal, of a bluifh grey colour, hard,ductile and malleable; capable of acquiringmagnetic polarity, and of being welded ; folublein the muriatic and moft other acids; precipi-table in the ftate of Pruffian blue by a pruffiatedalkali, and afluming a deep bluilh-black colourwith infufion of gall-nut.
Sp. r. Native Iron. Gediegen Eifen. Wern.Fer Natif. Broch.
Its colour is light fteel-grey refembling whitecall iron or platina; but it is generally coveredby a thin fuperficial cruft of brown oxvd. Itoccurs branched or cellular. Its luftre is mo-derately {tuning and metallic. Its fraCture ishackly; it gives a bright ftreak, may be eafilycut with a knife; and is perfe&Iy malleablewhen cold, and in a moderate heat, but at ahigh temperature it becomes brittle and granu-lar ; it is flexible and difficultly frangible. Sp.gr. not exceeding 6.48.
A mafs of native iron, reported by the inha-bitants of the country to have fallen from theIky, was found by Profeflor Pallas in Siberia .Between the rivulets Ubei and Siffim, that runinto the Jenifei on the eaftern fide, is a moun-tain containing a rich mine of magnetic ironore; on the fame fide of the mountain wherethis mine is fituated, was found lying loofe onthe rock the mafs of native iron alluded to,weighing 1680 Ruffi lbs. b This mafs is cel-lular, and the cells are either empty or occupiedby a tranfparent greenifh yellow fubftance, at firfttaken for fluor ipar, but which on fubfequentexamination greatly refembles the cliryfolite. c
A ftill larger mafs of native iron was feenand defcribed by Don Rubin de Cells. d It isfituated in the diftriCt of Otumpa, in the Vice-royalty of Peru ; its weight is about 15 ton;it is comp aft externally, and is marked withimpreffions as if of hands and feet, but muchlarger, and of claws of birds ; internally it is fullof cavities. It is almoft imbedded in white clay,and the country round is quite flat and deftituteof water. Another mafs of iron likened in
k Pallas in Phil. Tranf. lxvi. p. 513. * Bqurnon in Phil. '
liil. Tranf. Ixxviii. p. 183.
' 4 C
VOL. I.