IRON. 
six, without adding any fresh colour. 
These tints differed in regular gradation 
from greenish blue to green, olive green, 
yellowish green,, yellow, and so on to a 
buff. 
Concentrated nitric acid acts very 
strongly upon iron filings, much nitrous 
gas being disengaged at the same time. 
The solution is of a reddish brown, and 
deposits the oxide of iron after a certain 
time ; more especially if the vessel be left 
exposed to the air. A diluted nitric acid 
affords a more permanent solution of iron, 
ot a greenish colour, or sometimes of a 
yellow colour. Neither of the solutions 
affords crystals ; but both deposit the oxide 
of iron by boiling, at the same time that 
the fluid assumes a gelatinous appearance. 
Diluted muriatic acid rapidly dissolves 
iron, at the same, time that a large quantity 
of hydrogen is disengaged, and the mixture 
becomes hot. In this, as well as in the sul- 
phuric solution of iron, the same quantity 
of alkali is said to be required to saturate 
the acid as before the solution ; whence it is 
inferred, that the acid is not decomposed, 
but that the oxidation is effected by the 
oxygen of the water ; whence also it appears 
to follow, that the hydrogen must be af- 
forded from the decomposed water, and 
not from the metal. 
Carbonic acid, dissolved in water, com- 
bines with a considerable quantity of iron, 
m proportion to its mass. Vinegar scarce- 
ly dissolves it, unless by the assistance of 
the air. 
Phosphoric acid unites v-'.th iron, but 
very slowly. The union is best effected by 
adding an alkaline phosphate to a solution 
of one of the salts of iron, when it will 
fall down in a white precipitate. A sa- 
turated phosphate of iron has been found 
native in France, semi-transparent, of a red 
brown colour, and foliated texture. A 
deep blue phosphate of iron, lamellated, 
and fragile, of the specific gravity of 2.6, 
brought from the Isie of France, and ana- 
lysed by Langier, Fonrcroy, and Vauque- 
lin, gave iron 41.25, phosphoric acid 19.25, 
water" 31.25, alumina 5, and ferruginous 
silex 1.26, in 100 parts. A similar phos- 
phate has been found in Brazil. This acid 
is found combined with iron in the bog 
ores, and being at first taken for a peculiar 
metal was called siderite by Bergman. 
Liquid fluoric acid attacks iron with vio- 
lence; the solution is not crystallizable, but 
thickens to a jelly, which may be rendered 
solid by continuing the heat. The acid 
may be expelled by heating it strongly, 
leaving a fine red oxide. 
Borate of iron may be obtained by preci- 
pitating a solution of the sulphate with 
neutral borate of soda. 
Arsenic acid likewise unites with iron. 
Tliis arseniate is found native in Cornwall, 
in pretty large cubic crystals, tolerably 
transparent, of a dark green colour with a 
brownish tinge; sometimes yellowish, or of 
a brown yellow, like resin. The Count de 
Bournon found likewise a cupreous arseniate 
of iron, in minute rhomboidal crystals of a 
faint sky blue colour and uncommon bril- 
liancy. Specific gravity 3.4. The green 
and. red sulphates of iron may be decom- 
posed by arseniate of ammonia, and afford 
arseniate of iron in the two different states. 
Chromate of iron is said to have been 
found abundantly in the department ofVar 
in France, and to form a beautiful green for 
enamelling or colouring pastes. Its analysis 
by Vauquelin and Tassaert gave chromic 
acid 43, oxide of iron 34.7, alumina 20.3, 
silex 2, in tOO parts. 
In the dry way, this metal does not com- 
bine with earths, unless it be previously 
oxided ; in which case it assists their fusion, 
and imparts a green colour to the glass. 
It appears to combine with alkalies by 
fusion. Nitre detonates strongly with it, 
and becomes alkalized. 
Sulphur combines very readily with iron, 
in the dry and even in the humid way, 
though neither of these substances is scarce- 
ly at all soluble in water. A mixture of 
iron filings and flowers of sulphur being 
moistened, or made into a paste, with wa- 
ter, becomes hot, swells, adheres together, 
breaks, and emits watery vapours of an 
hepatic smell. If the mixture be consider- 
able in quantity, as for example, one hun- 
dred pounds, it takes fire in twenty or 
thirty hours, as soon as the aqueous vapours 
cease. 
By fusion with iron, sulphur produces a 
compound of the same nature as the pyrites, 
and exhibitin'g the same radiated structure 
when broken. If a bar of iron be heated 
to whiteness, and then touched with a roll 
of sulphur, the two substances combine, 
and drop down together in a fluid state. 
It is necessary that this experiment should 
be made in a place where there is a cur- 
rent of air to carry off the fumes ; and the 
melted matter, which may be received in 
a vessel of water, is of the same nature as 
that produced by fusion in the common 
way, excepting that a greater quantity of 
