502 Metals. MINERALOGY. Metals. 
able in the refra&ion of light by flint-glafs 5 and M. Hally 
thinks that flint-glafs derives the property of thus dif- 
perfing the rays of light from the oxyd of lead, which is 
one of its conftituent parts. This form of lead occurs 
more commonly than any other, except the fulphuret; 
but rarely in fufficient quantity to be worked on a large 
fcale. It generally accompanies galena, or fulphuret of 
lead, and ores of zink. 
In the Annales de Chimie for 1811, there is an account 
of the procefs for making the Blanc de Krerns, or car- 
bonat of lead ; which, as a proper fupplement to the dif¬ 
ferent preparations of lead given under the article Che¬ 
mistry, we lhall here infert. 
“ The Blanc de Krems was firft made in the town of 
that name; but for a long time none has been made there, 
and the greateft manufaftory of it is at Klangenfurt in 
Carinthia. The lead ufed in it comes from Bleiberg, near 
Willach, in Carinthia; it is very pure, and contains no 
ferruginous oxyd, or even filver. 
“ The firft operation confifts in forming the lead into 
thin plates, which is done by pouring it in a ftate of fu- 
fion on an iron plate placed above the cauldron, which, 
as loon as the furface of the metal begins to confolidate, 
is inclined a little to let the liquid lead fall back into the 
cauldron, and there remains a rough plate on the plate 
of iron, which in fome manufactories is half a line thick, 
and in others only one quarter of a line; the roughnefs 
of the furface dilpofes the plate better to admit the action 
of the acid. Thcfe lheets of lead are then doubled, like 
the leaves of a book, acrofs fmall pieces of wood, which 
are placed acrofs wooden cafes, which vary in different 
places from five feet in length to four and a half, from 
one foot to one foot two inches in breadth, and from nine 
to eleven inches in depth. The fheets are not fullered to 
touch each other in the cafes. The bottom of each of 
tliefe cafes has a bed of pitch laid on it about an inch 
thick ; and they are luted with paper, when the ftove is 
not heated by fleam. Juft before the fheets of lead are 
put into the cafes, a mixture of four pints of vinegar to 
four pints of wine-lees is put into each; but in fome 
J daces the mixture confifts of twenty pounds of wine- 
ees, eight and a half of vinegar, and half a pound of car- 
bonat of potafh. The cafes are then placed in a ftove, 
which is warmed by two furnaces, and contains ninety 
cafes one of thele ftoves meafures nine feet high, four 
fathoms wide, and five fathoms long. The heat never is 
buffered to exceed 30 of Reaumur, and is continued fif¬ 
teen days. The mixture will ferve but once; and the 
lead ufually produces its own weight of carbonat of lead, 
with a confiderable furplus of lead, which is melted 
again. 
“ When the plates are taken from the cafes, they are 
found to be increafed in thicknefs to a quarter of an inch 
or more, though at firft but a quarter of a line; they are 
violently fliaken, and the carbonat that falls from them 
is received in large tubs, where it is purified by wafhing 
in the following manner: A large fquare tub is prepared, 
divided into from feven to nine compartments, equal in 
capacity, but unequal in height, fo that thole which are 
too full run into the next. The water which is poured 
into the firft, runs fucceflively into the others, being agi¬ 
tated a little at the fame time ; it depofits proportionally 
the white in each compartment, and that in the laft is the 
fineft and whiteft. The white-lead is after this waflied a 
fecond time in larger tubs, and left in the water, where 
a white fcum rifes to the top, fuppofed to be an acetat 
of lead, from which fome carbonat is precipitated by 
potafh. From the tubs the white-lead is taken out in a 
liquid pafte with a wooden fpatula, and depofited on 
dryers, where it foon acquires the confidence of a foft 
pafte, and is then put into moulds to give it a convenient 
form for bale. 
“ The carbonat of lead, thus formed, is mixed with 
other lubftances, by which various forts are produced. 
The firft fort, or fineft, is that depofited in the laft divi- 
fion of the wafhing-veflel, without any mixture, and fold 
under the name of Kremjerweifs, filver-white, and blanc 
de krems. The fecond fort is formed by mixing equal 
parts of fulphat of barytes with the carbonat of lead : in 
Germany it is called Venerianerweijs, or Venice white. 
The fulphat of barytes is brought principally from the 
Tyrol, and fome of it from Syria; the former is the belt, 
as it contains no oxyd of iron. To pulverife it more 
eafily, they ufually calcine it, which makes the oxyd of 
iron have more efteft; in fome places they now ceafe to 
calcine it for this reafon. The third fort confifts of a 
mixture of two parts of fulphat of barytes to one of the 
carbonat; and is called Hamburgh white. The fourth 
fort is formed by mixing three parts of the fulphat with 
one of the carbonat; this is called Dutch white. A 
cheap fort is made by putting feven parts of the barytes 
to one of the white-lead, and fold by the fame name. 
The barytes is ufeful in making the lead cover a fur¬ 
face when laid on with a bruih, which it will not do well 
alone. 
“ The barytes is pulverifed in a pounding-mill, on a 
plate of iron pierced with holes, through which it falls 
into veflels placed to receive it; after this it is mixed 
with the white-lead, and ground in a horizontal hand- 
mill, made on the fame principle as a common flour-mill, 
into which the mixture is put through a hole in the 
centre of the upper ftone: the motion is given to the 
mill by a pole, the top of which is inferted through a 
ring, placed exaftly over the centre of the ftone ; and its 
lower end, terminating in an iron pin, moves in a hole 
made for it on the top of the upper ftone, near its cir¬ 
cumference: by grafping the pole lower down or higher 
up, the workman increafes the power or the velocity of 
the motion as he pleafes. In the figure annexed to the 
defcription, the top of the mill is not higher than half 
the height of the workman: it is furniflied with a lever 
and lcrew for raifing or lowering the upper ftone, in the 
fame way as done in common mills ; but, to prevent the 
liquid from running out at the hole of the lower ftone, 
through which the fpindle pafles to the upper one, a 
piece of wood is inferted in it, having an aperture for 
the fpindle that fits it more clofely; and it is farther 
fecured by a piece of woollen cloth. Half a day is al¬ 
lowed for the complete mixture of a hundred pounds of 
the colour.” 
The fubftance mixed in this country with white-lead 
is chalk, inftead of the barytes above-mentioned; which 
accounts for fome white paint having the power of de¬ 
fending fliips from the attacks of the worm, and other 
kinds not having this quality, the fulphat of barytes 
being of a much more poil'onous quality than the lead. 
As barytes is much heavier than chalk, and is found in 
various parts of Britain, it is probable it will ultimately 
be ufed by our white-lead manufafturers. Great care 
fliould be taken never to ufe the calks in which this co¬ 
lour has once been, for any article of food, molt melan¬ 
choly accidents having happened from carelelfnefs in 
this refpeft; one infcance, lately publifhed, mentions four 
in one family having died from ufing fugar put in a calk 
of this kind. 
7. Plumbum hyalinum, or murio-carbonat of lead: 
tranfparent, eft'ervefcing with nitric acid, foft, decrepi¬ 
tating on red-hot coals, of a glofl'y luftre, in the form of 
cryftals. Found in the mines of Derbylhire and the Hartz, 
in cryftals, the primitive form of which is a cube, often 
lengthened, with the edges generally truncate and re¬ 
placed by fmall planes. Colour from a clear tranfparent 
white to a pale Itraw-yellow, with a luftre much exceed¬ 
ing that of the laft: texture glafl'y, rd'embling that of 
recious ftones. It is foft enough to be fcratched by car- 
onat of lead. Contains oxyd oflead 85, muriatic acid 8, 
carbonic acid 6. Chenevix. 
8. Plumbum flavum, yellow lead-ore, or molybdat of 
lead : yellow, in the form of cryftals ; foft, decrepitating 
before the blowpipe: foluble in muriatic and fulphuric 
a acidsj 
