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grains to a fcruple. It has been ufually diftinguilhed in the 

 (hops by the name of its inventor, Dr. Willis. 1 1. " Li- 

 quor ferri alkalini," or folution of alkaline iron, is compofed 

 of 2{ drams of iron, two fluid-ounces of nitric acid, fix 

 fluid-ounces of dillilled water, and fix fluid-ounces of the fo- 

 lution of fubcarbonate of potafs. Having mixed the acid and 

 water, pour them upon the iron, and when the efFervefcence 

 has ceafed, pour off' the clear acid folution ; add this gradually, 

 and at intervals, to the folution of fubcarbonate of potafs, 

 occafionally fliaking it, until it has an"umed a deep brown- 

 red colour, and no farther eff'ervefcence takes place. Laftly, 

 fet it by for fix hours, and pour off the clear iulution. This 

 preparation was firil defcribed by Stahl, and calKd " tinftura 

 martis alkalina," and it is for the firil time introduced into 

 the London Phamacopeia of 1809, as affording a combina- 

 tion of iron diftinft from any other, and often apphcable to 

 praAice. It feems to be a triple fait, formed by the union 

 of nitric acid with red oxyd of iron, and with potafs. Dr. 

 Lewis has obferved, that alkaline folutions of iron are ill 

 adapted for medicinal ufe; and on that account, he fays, they 

 have been wholly neglefted in modern praftice. 12. " Vi- 

 num ferri," wine of iron, P. L. 1787 and 1809, " Vinum 

 chalybeatum," P. L. 1745, confifts of two ounces of iron- 

 filings mixed in two pints of wine. The mixture is fet by 

 for a month, occafionally fliaking it, and it is then filtered 

 through paper. Lewis Mat. Med. CuUen Mat. Med. 

 London Pharmac. 1809. See Chemical Properties ef luoN, 

 Chalybeate), and Mineral, &c. Waters. 



Irox, Cafe-hardening of, a procefs by which a fuperficial 

 hardnefs is given to various articles made of iron. It is 

 found by experience that pure iron is not fufceptible of a 

 very fine pohfli, and that, when it is expofed to the air, it 

 very foon changes. All iron utenfils, therefore, fuch as fire 

 irons, and many other articles, having the appearance of 

 poliihed ileel, are cafe-hardened, for the purpofe of giving 

 them a finer polifli, as well as rendering their colour mtire 

 permanent. The goods to be cafe-hardened fhould be finidied 

 with the exception of polifhing, fince, if the procefs be well 

 managed, the moil delicate workmanfliip will not be injured. 

 A box of wrought iron muft be provided, which iis perfedlly 

 found in every part, having a lid of the fame metal, to fit 

 very tight. In this box the articles are to be fl;ratified with 

 powdered carbon, that of animal fubilances being the beft, 

 for reafons given in the article Irox, in the feftion on Steel. 

 The box being perfeftly filled with thefe materials, let the 

 lid be fitted on, and luted all round with a palle made of 

 equal parts of pipeclay and Calais fand. The whole is now 

 to be furrounded by bricks loofcly built up, a little higher 

 than the top of the box, leaving about four inches on each 

 fide for fuel. This may be done either upon a fmith's 

 hearth or in the open air. The moft proper fuel is the re- 

 fufe -cokes from any fires where pit -coal is burnt. The fire 

 being kindled, and the fpace filled up with this fuel, the heat 

 will be applied gradually, owing to the fmothered combuf- 

 tion. As foon as the box appears of a light red heat, let it re- 

 main about half an hour, or more time if the box be large, in the 

 fame temperature. The lid may now be taken off, and the box 

 inverted and its contents emptied over a ciftern of cold water. 

 If the box be fuffered to cool without being opened, the 

 goods will be perfcdlly white and metallic when taken out. 

 If they are now heated red-hot, and quenched in cold water, 

 they acquire the fame hardnels as if turned out of the box 

 red-hot into the water. If the articles are very delicate, fo 

 as to be injured by the air in heating a fccond time, they 

 may be preferved, by dipping them into a mixture of a fatu- 

 rated folution of fait (muriate of foda) with any vegetable 

 matter to give it a pulpy confiflence. During the time of 

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heating it red-hot, the fait fufes upon the furface of the 

 metal, defending it from the oxygen, fo that after it is 

 quenched in the water, and bruflied, it will be perfeftly 

 clean. 



The fize of the iron box fhould not be very large ; it is 

 better to do the work at two or three proceffes. Charcoal 

 is a very bad conduftor of heat, and if the mafs to be heated 

 were large, thofe articles near the fides would be over done, 

 by combining with too much carbon, while thofe in the mid- 

 dle would be too little carbonated. 



People in the habit of cafe-hardening, have generally 

 fome feeret receipt for the procefs, on which they fet great 

 value. All, however, agree in ufing carbon, the only thing 

 neceffary : fome iidd to this falt-petre ; others fal ammoniac, 

 and other articles, to which they very knowingly attribute 

 their relative fuccefs. We can, however, afl^ure the moft 

 fage of thefe perfons, that if they make their box perfectly 

 air-tight, by the rules above given, ilratifying the articles 

 with animal carbon alone, they will, with proper heat and 

 time, produce the greatell pofTible eft'eft. 



Animal carbon may be produced from mofl; animal fub- 

 fl;ances : among thefe are blood, hoofs, and leather. Thefe 

 fubilances Ihould be preffed into an iron pot, which can be 

 heated red-hot, covered clofe, with a fmall open tube infert- 

 ed into the cover. The volatile matter that efcapes may be 

 fet on fire, « hich will in a gieat meafure dellroy the fmell ; 

 or a receiver may be adapted, and the crude ammonia dillilled 

 off. When the volatile fubilances have come over, the re- 

 fiduum will be fine animal carbon, which requires only to be 

 reduced to powder. 



This animal carbon is fo fitted for combining with iron, 

 that if it be made into a pulp with a faturated folution of 

 fait, and laid upon the furface of iron ; upon being heated 

 red-hot, and quenched in cold water with this coating upon 

 it, the furface will become hard. Any part of an iron ar- 

 ticle, not wifhed to be cafe-hardeneJ, may be prevented from 

 undergoing the i hang", by covering the pan with pipe-clay. 



I R 1 N , For the blueing of, fee B 1 u El N G. 



Iron, For the expanfion oj, by heat, fee Heat and Pyro- 

 meter. 



Iron Chambers. See Chambers. 



Iron, For the refining of. See Refining and Iron, § 4. 

 fupra. 



Iron, For the converfion of, into fleel. See Iron and 

 Steel. 



Iron Furnace. See 'Ri.Pi.&T-Furnace, and Iron, fupra. 



Iron, harping. See Harping. 



\KOTf.-Uquor, in Calico Printing and Dyeing, is a folution 

 of iron in the acetic acid, ufed as a mordant for certam colours. 

 It is employed as a fubftitute for the fulphat of iron, and is 

 preferred, in thofe proceffes, to the lall fait. The oxyd of 

 iron, which is the effential ingredient, is more eafily attraft- 

 ed by the Huff from the acetic than the fulphuric acid, and, 

 befides, the texture is not fo liable to be injured by the ace- 

 tat as the fidphat of iron. In order to make this fubllance 

 cheap, the acid dillilled from wood, called pyrolignic acid, 

 and now tound to be impure acetic acid, is uied as a fubfti- 

 tute for vinegar. See PvROLiGNic ^cid, and the lail fec- 

 tion of the article Iron. 



Iron moulds are marks or ftains produced on fubilances, 

 particularly linen and cottou, by the oxyd of iron. The 

 affinity of thefe vejietable fubilances for the oxyd of iron is 

 fo great, as not only to take it from the furface of iron, but 

 from any acid with v,>hich it may be combined. We find, 

 hence, that very few acids are capable of removing iron- 

 moulds. From the well-known faCl that the attraftion of 

 acids for oxyds of metals is more feeble as the latter contain 



more 



