C H E M I 
smelts by a moderate heat into corneous lead, and is to¬ 
tally foluble in water. This mats was employed by 
Margraaf in the procefs for making the pholphorus of 
urine. The red oxyd of lead afts in the fame manner 
with mlariat of ammoniac in the cold j for, as foon as the 
mixture is made, the ammoniac begins to come over. 
The femi-vitreous oxyd of lead decompofes muriat of 
foda : Take four parts of this oxyd and one of muriat of 
foda; reduce the oxyd to powder, and diffolve the mu¬ 
riat in four times its weight of water ; mix the two fub- 
Itances together into a light pafte. Thus let it remain ; 
and, when the furface begins to whiten, work it with a 
wooden fpatula : if it acquires too much folidity, dilute 
it with frelh quantities of the folution of muriat of foda; 
if there is not enough of this folution, then ufe common 
water. At the end of a few days.the decompofition is 
complete j and the refult is a homogeneous pafte, very 
white, without clods. To feparate the foda, dilute the 
pafte in a fuffkient quantity of boiling water, ftirring the 
mixture continually; for otherwife the pafte will clod, 
and the lixiviation becomes very difficult. Draw off the 
floating liquor of foda by decantation, and feparate the 
reft of the alkali by filtration and expreffion with a cloth : 
then evaporate the liquor in iron veffels, and thus the 
foda will remain dry. By calcining the other product of 
this operation, which is muriat of lead, it gives a yellow, 
ftrong, bright, colour, which may be 1'uccefsfully ufed 
with oil. 
Muriat of lead may be decompofed alfo with fulphuric 
acid weakened to 25 0 ; a fulphat of lead is the refult, ve¬ 
ry white, and in a ftate of extreme divifion and finenefs. 
Wafli it in a great deal of water; triturate it very care¬ 
fully till it gets a certain confiHence ; then dry it. This 
white colour may be liiccefsfully ufed in painting, and 
never grows yellow with oils. The grey oxyd of lead 
mixed with fuper-oxygenated muriat of potalh, and laid 
in a heap, will detonate by an eleftric fhock. 
Lead is ufed in a great number of works. It forms a 
part of many alloys, and is made into pipes for the con¬ 
veyance of water. Its oxyds are employed in glafs-mak- 
ing, and in the preparation of enamels. It is ufed to 
imitate the colour of yellow precious Hones, and to give 
fufibility to the glaze of earthen ware. Utenfils and vef¬ 
fels proper for economical ufes are made with this metal, 
but not without danger in their ufe. Fountains, or vef- 
fels of lead, in which water is buffered to remain a long 
time, often communicate a noxious quality to it. Its 
vapour is dangerous to the workmen who melt it, and 
its tafte is Hill more dangerous to fuch as file and fcrape 
it. This metal, lodged in certain parts of the ftomach 
and inteftines, produces violent colics, often accompa¬ 
nied with vomiting a very brown bile, and characterized 
by the flatnefs of the belly, .and linking of the navel. It 
has been obferved, that, in fuch cafes, antimonial eme¬ 
tics and purges have been attended with great fuccefs. 
Wavier advifes the different alkaline fulphures in cafes of 
poifoning by the preparations of lead, as well as in fuch 
as are produced of arfenic and corrofive mercurial muriat; 
and it is more particularly in the pally and tremblings 
which commonly remain after the colica pittcnum, or 
painters colic, that this phyfician boafts of the good ef¬ 
fects of alkaline fulphure and fulphureous waters. At 
all events, when thelefafts are duly confidered, we ought 
to avoid the internal ufe of preparations of lead, and 
only apply it as an external medicine; and even in this 
laft cafe it ought not to be adminiftered but with all that 
care and caution which are required in the ufe of a ftrong 
repellent. 
Of IRON. 
This metal, called Mars by the alchemifts, is very abun¬ 
dant in nature, under different modifications. Various 
terreftrial fubftances, contain it in the form of grains 
which may be extracted ; and in a Brill greater number 
it is a colouring, principle. Pure iron is foft, and foft 
Von. IV, No. 197. 
S T R Y. 297 
iron is duCtile. Caft iron is that which has been feparated 
from its ore, and rendered fufible by a fmall quantity of 
charcoal and a certain proportion of oxygen : there are 
three forts, black, white, and grey. 
Steel is iron, which, after being caft, is become duCtile 
by hammering ; then it is made to re-abforb the charcoal 
it retains, which greatly increafes its weight; it acquires 
another property alfo, temper. The temper does not in- 
creafe the denfity of the iron. By touching fteel with 
an acid, there is a black fpot, which is not the cafe with 
iron. The procefs for converting iron into fteel, is as 
follows : Short bars of iron are ericlofed in an earthen 
boxorveffel, filled with a cement, commonly compofed 
of very combuftible matters, fuch as foot, or the coal of 
animal matters, animal oil, to which is ufoally added, 
allies, calcined bones, marine fait, or fal-ammonias. 
The box, being well doled, is heated for ten or twelve 
hours, till the bars become white, and are ready to melt. 
In this operation the iron becomes purified, and is com¬ 
pletely reduced by the affiftance of the combuftible mat¬ 
ters with which it is furrounded; the portions which 
were not perfectly in the metallic ftate,' affume that ftate; - 
and the phofphure of iron, if it ftill remains, appears to 
be entirely decompofed. The iron being foftened and 
dilated, abforbs the charcoal which l'urrounds it; and 
hence the fteel of cementation is nothing elfe but a com¬ 
bination of pure and well-reduced iron with charcoal. 
It differs from iron in containing charcoal, and from caft 
iron in this, that the crude iron contains not only char¬ 
coal, but a greater or Ids quantity of oxygen. If call 
iron be deprived of its oxygen without leparating the 
charcoal, or by giving it a new quantity, fteel will be 
produced without refining the iron. Clouet lays a i-32d 
part of charcoal is fufficient to convert iron into fteel. 
In a quantity equal to one i-6th of the iron it affords a 
fteel more fufible and ftill malleable, but beyond this 
term it approaches to caft iron, and has not a fufficient 
degree of tenacity. Steel-is much more fufible than iron, 
for which reafon the bars which are converted into fteel 
by cementation, are foftened to that degree, that the 
carbonic acid, which is difengagedin bubbles during the 
adlion of heat, forms fmall buffers, or very fenfible cavi¬ 
ties, on its furface. This kind of fteel is called blijler 
Jleel. The differences of fteel depend upon the greater 
or lefs reduftion of the iron, the quantity of charcoal 
which it contains, and the more or lefs ludden cooling 
it has been fubjefted to. The quantity of charcoal con¬ 
tained in fteel may be afcertained by pouring fulphureous 
acid over the metal: the iron and the fulphur remain in 
folution, and the carbure of iron is precipitated ; by dry¬ 
ing this laft fait, the quantity of charcoal will be known, 
as the proportions of the conftituent parts of carbure of 
iron are well known. 
A new method of preparing caft fteel has been lately 
announced in France by Clouet. His procefs is the fol¬ 
lowing: Take fmall pieces of iron and place them in a 
crucible, with a mixture of carbonat of lime and the 
earth of Heflian crucibles, fix parts of the carbonat of 
lime, and fix of this earth, muff be employed for twenty 
parts of iron. The mixture is to be dilpoled fo, that af¬ 
ter fufion the iron may be completely covered by it to pre¬ 
vent the iron from coming into contadl with the external 
air. The mixture is then to be gradually heated, and at 
laft expofed to a heat capable of melting iron. If the 
fire be well kept up, an hour will generally be fufficient 
to convert two pounds of iron into excellent and exceed¬ 
ingly hard fteel, capable of being forged; an advantage 
not poffeffed by fteel in the common manner. The oxyds 
of iron are equally lufceptible of paffmg to the ftate of foft 
iron, fteel, and caft iron, according to the quantity of 
carbon employed. The black oxyd, the ftate of which 
fee ms to be the moft unalterable, becomes iron when 
treated in the crucible with an equal volume of charcoal 
duff. By doubling the .quantity of the charcoal, fteel is 
formed, and a progreflive increafe gives it the thara&ers 
4 G of 
