2 9 -8 C HEM' 
of white and grey caft iron. A fifth part only of call 
iron is required to convert iron into fieel. The iron and 
the oxyd do not unite intimately. The black oxyd, 
mixed with one half lefs of carbon than is neceffary for 
its redu&ion, gives a foft iron, but not very tenacious, 
black, and without a granulated fradlure. A fixth part 
of. the oxyd brings back common fteel to the ftate of 
iron, by treating them together, either in the forge or by 
cementation. 
Magnetifm is a charadleriftic of iron ; it appears every 
where, even in ftone, in marble, and in bodies where it 
exiftsin very fmall quantities, and is only a colouring 
principle. In the green marble of Campan it attradls the 
magnetic needle; in the green marble it does not, 
though that contains more iron ; but in this la ft it is 
.more oxydated. 
Iron has a confiderable fmell, efpecially when rubbed 
or heated. It likewife has a very evident ftyptic tafte, 
which afts ftrongly on the animal economy. Next after 
tjn, it is the lighted of metallic fubftances ; a cubical foot 
of this metal, when forged, weighs 580 pounds. It may 
be extended into plates by beating; but as it is very 
hard, and becomes ftill harder under the hammer, it 
cannot be made into leaves. Its dudlility, when drawn 
into wire, is much more confiderable; very fine wires be¬ 
ing made of this iubft.mce formufical purpofes : this pro¬ 
perty appears to depend on its tenacity. In fadl, iron'is 
the molt tenacious of all metals, except gold. An iron 
wire, of one tenth of an inch in diameter, fuitains a 
weight of 450 pounds without breaking. Another lingu¬ 
lar property is that of taking fire, or fuddenly melting, 
by the ltroke of a flint; a phenomenon to which the 
poets univerfally attribute the difcovery of fire by the 
firft men. Another property which diltinguilh.es it is, 
that it is found with manganefe in plants and animals, 
whole fluids it partly colours. It is likewife lufceptible 
of a regular form, or cryftallization. If iron-filings be 
thrown on burning coals, or even through the flame of a 
taper, it fuddenly takes fire, and produces very brilliant 
fparkles. Thefe are fimilar to thole produced by the 
ftroke of the Iteel againft flint, and if colledted on a white 
paper, they are found to be melted, and relemble a kind 
of fcoriae. This metal, expofed to the focus of the lens 
of De Trudaine, fuddenly throw's out inflamed and burn¬ 
ing fparkles. Macquer, who melted fteel and iron in 
this lens, obferved, that fteel was the molt fufible, which 
arifes from its combination with charcoal. Iron melted 
and fullered to cool llowly, takes a peculiar cryftalline 
form ; Mongez deicribed it to be a pyramid of three or 
four fides. 
The blow pipe, with vital air, caufes the filings of 
iron to burn as rapidly as the focus of a lens. If an iron 
wire turned in a fpiral form, and terminated by a fmall 
piece of lighted quick match, be plunged into a vefiel of 
vital air, thejnetal fuddenly catches fire, and bums with 
a very remarkable degree of rapidity and deflagration. 
In all thefe fufions, the iron becomes brittle and is oxy- 
dated, at the fame time that it aflumes a black colour. 
Iron, though very hard and refraftory, is very eafily cal¬ 
cined or oxydated ; when it begins to grow red, it com¬ 
bines with the oxygen, and burns without any apparent 
flame. A bar of iron kept red hot for a long time, be¬ 
comes covered with fcales, which may be beat oft’ with 
the hammer. In thefe, however, the metal is only partly 
oxydated, fince they are attradlable by the magnet. A 
more perfedl oxyd of iron is made, by expofing filings 
of fteel, and ftill more quickly the fcales of hammered 
iron, to heat under a muffle. They are converted into a 
reddilh brown powder, not attradlable by the magnet, 
and called afringent faffron of Mars. We call it the red 
oxyd of iron, and the fcales the black oxyd, ox hammerings. 
This laft fubftance contains from twenty to twenty-five 
per cent, of oxygen ; the red oxyd contains from thirty- 
jwo to thirty-four. 
The purelt iron expofed to moilt air, foon lofes its me- 
S T R Y. 
tallic brilliancy, becomes covered with a pulverulent cruft, 
of a yellow brown colour. This matter is ufually called 
rujl. Common iron is much more fubjedt to ruft than 
fteel; the more this metal is divided, the more rapid is 
its alteration by expofure to air. In this manner the pre¬ 
paration, known in pharmacy under the name of aperi¬ 
tive faff r on of Mars, is prepared. Iron-filings are expofed 
to the air, and moiftened with water, by which means 
they very quickly ruft. Then pulverife the filings in an 
iron mortar ; a yellowilh dull appears ; this is to be fepa- 
rated by lifting through lilk, and will be found to be the 
faffron of Mars, or rather a combination of the oxyd of 
iron with carbonic acid. 
Iron may be united with phofphorus: mix equal parts 
of phofphoric glafs and iron in chips, with one-eighth 
part of charcoal; melt the whole in a crucible, and the 
button v/ill be found very brittle, white in its fradlure, 
with a ftriated and granulated appearance; fometimes 
cryftallized in rhomboidal prilms: this is phofphure of 
iron. If this phofphure be heated with the blow-pipe, it 
produces a phol'phorous flame. The exiftence of phof¬ 
phorus in forne fpecies of fteel, is fully afcertained by the 
following experiment of Vauquelin; 576 grains of fteel 
filings were difi'oived in fulphuric acid, diluted with five 
parts of water. From this folution, laturated with car- 
bonatof potalh, nineteen grains of a white taftelefs pow¬ 
der were depofited, completely foluble in muriatic acid. 
This matter, by boiling it in a folution of cauftic foda, 
aflumeda deep red colour, and was greatly diminilhed in 
its volume. The liquor being filtered, and mixed with 
concentrated muriatic acid, gave no fign of effervefcence ; 
and formed, before and after its mixture with muriatic 
acid, a white precipitate, by the addition of lime water. 
On examination thisprecipitate was found to bephofphat 
of lime. 
Charcoal unites with iron, forming carbureof iron, or 
plumbago. Carbure of iron is of a finning blue black, of 
a greafy feel, and tuberculated fradlure; it foils the 
hands, and makes a black trace on paper. It is not al¬ 
tered by fire in clofe veflels: Pelletier, who has made 
experimental inquiries on this fubftance, which confirm 
the refultsof Scheele, expofed 200 grains in a porcelain 
crucible, accurately clofed, to the heat of the furnace of 
the manufactory ofSeve; the lofs was no more than ten 
grains. But, when heated with coiltadl of air, it burns, 
and is oxydated, leaving fcarcely any refidue. Quill, 
Gahn, and Hielm, obferved, that one hundred grains, 
treated in this manner, in a muffle, left only ten grains 
of ferruginous oxyd. This oxydation is a flow combuf- 
tion, not eafdy performed. It does not fucceed in a com¬ 
mon crucible: a thin layer of carbure of iron muft be 
expofed, in a fhallow vefiel, to the action of aftrongfire, 
and the furfaces muft be often renewed, by ftirring the 
matter. It is in this way that the carbure of iron em¬ 
ployed to cover Hones, See. is gradually burned. 
Air, water, and earthy fubftances, have no adlion on 
carbure of iron. Alkalis add ftrongly on this fubftance. 
If one part of carbure of iron, with two parts of dry 
cauftic fixed alkali, or lapis cauflicus, be expofed to heat 
in a retort, with the pneumatic apparatus, the fmall 
quantity of water contained in the fait is fufficient to fa¬ 
vour the combuftion: carbonated hydrogen gas is ob¬ 
tained, the alkali is charged with carbonic acid, and the 
carbure of iron is found to have difappeared. Among 
the acids, only the muriatic ferves to purify it, becaule 
this aciddiffolves all the fubftances with which it is com¬ 
bined. 
We have feen that iron readily abforbs charcoal by 
heat, and that it forms caf iron and feel by its union 
with this coinbuftible fubftance; with this difference, 
however, that it contains oxygen in the former of thefe 
compounds, but not in the latter. In both, the quantity 
of iron greatly exceeds that of the charcoal. Chemical 
analyfis, which is fo much indebted to the labours of 
Scheele, has proved to this chemift, that plumbago, a mi¬ 
neral 
