£46 
takes the name of Yellow or Burgundy 
Pitch, Poi« Faune, Poix de Bourgogne. 
~ YELLOW ROSIN. (Refa Faune.) 
This is made with galipot, and in the 
fame veficl. Itis liquefied with a gentle 
heat, being often ftirred to prevent burn- 
ang, and evaporated to the requifite con- 
fiftence, and paffed through a ftraw filter. 
itis them biack, but this colour is taken 
away by adding to it eight or ten pints of 
boiling water, and ftirring it conftantly 
till cold. It acquires by this operation 
the fine yeilow colour for which it is fo 
guuch efeemed. It is then caft intc mejds 
‘for fale. | 
BLACK PITCH. {Pox Noire.) 
This is made out of the refule of refin 
and turpentine, fuch as will not pals 
through the ftraw filter, and the cuttings 
around the incifion on the tree. Thefe 
materials are put into a boiler hx or feven 
feet in circumference, and eight or ten 
high. Fuel is laid around the top, and 
the materials as they melt fow through a 
channel cut in the fire-place into a tub 
half filled with water. It is at that time 
very red, and almoft liquid. ‘To give this 
a proper confiftence, it is putin a cauldron 
placed ina furnace, and boiled down ia the 
fame manner as rofin, but it requires 
ruck lefs precaution and double the time. 
It is then poured into moulds of earth, 
and forms the beft kind of black pitch, 
pox nare. 
~. 
BRAY GRAS, and BASTARD PITCH 
(Pox batarde.) 
Bray Gyas ts a mixture of equal parts 
of bray fec, or colophony, of black pitch 
and tar (goudren). They are boiled dowa 
together and put into barrels of pine wood, 
forming a fubitance of a very liquid con- 
_fiftence, and called dray gras. ~ If, on the 
contrary, itis dered ot a thicker contift- 
ence, a greater proportion of colophony is 
added, and it.iscalt inmolds. It is then 
called porx batarde. : 
Hence it appears that there are three 
kinds of pitch in commerce, of which the 
firft (poix noire) thould be preferred for 
- pharmacy, being blacker and more brittle. 
Tak (Goudron.) 
To make tar, trees already exhaufted 
by incifions are taken, the wood is cut in 
{mall pieces and fuffered todry. They 
are generally cut in the winter and not 
ufed till the fummer, that feafon being the 
beft for making tar. The wood thus pre- 
pared is put on the hearth of a furnace of 
the fnape of a truncated cone, and piled 
up ina conical heap, and on the outfide 
Pitche-Tar—Verdigris. 
March 1, 
s 
of the centre cone another heap, inclofing 
the former, and fo on till the fire-place is 
full, when the top is covered with turf, 
and the wood kindled on allfides. As it 
heats, its refin filters downwards upon 
the hearth of the fire- place, and is collected 
in a hollow in the middle, whence a fub- 
terranean pafiage leads to an external re- 
fervoir. Thig tar'is called goudron de 
Chaisfe, becaufe it is packed up in bar- 
rels made of chefnut wood, which ceme 
from that place. ) 
Seven or eight days are required for each 
operation. ; 
Tar is alfo procured, and with more 
advantage, from the roots and fuckers of 
the fame trees. It is made in the fame 
manner and is more efteemed, but it re-, 
quires that thefe roots fhould lie expofed 
tothe air for ten or twelve years after they 
are cut. 
There is alfo another way of making 
tar from ‘larger pieces of wood, about 
five or fix fect long. The pitch-furnace 
is filled with them, and they are thea fet 
on fire, but this tar is lefs efteemed than 
the other, being harder. This method 
is therefore only ufed when there is not 
wood enough to fill the tar-furnace. 
On the Method of manufacturing Cryftal- 
lized Verdegris. By CaapTat. Annales 
de Chimie, Na. 75. . 
The procefs at Montpellier confifts in 
preparing a vinegar by diftillation of four 
wine: thisis put into a kettle,-and boiled 
on the common verdegris. After fatura- 
tion the folutiom is left to clarify, and then 
poured into another kettle of copper, where 
it is evaporated till a pellicle forms on the 
furface. Sticks are then immerfed into it, 
and by means of fome packthread are tied 
to fome wooden bars that reft on the edge 
of the Kettle. Thefe fticks are about 3 
foot long, and are fplit crols-wife nearly 
two inches at the end, fo that they open 
into four branches, kept at abont the dif- 
tance of an inch from each ether by finall 
bags. he cryftals adhere to theie flicks 
and cover them entirely, forming theme 
felves into groups or clulters of a dark 
blue colour, and a rhomboidal fhape. Each 
clufter weighs from five to fix pounds. 
Three pounds of moift verdegris are re- 
quired for one pound of the cryftals; the 
undiffolved refiduum is thrown away. 
The acetous acid is not capable ot acting. 
upon copper, except in the ftate of oxide; 
the defideratum then is to oxidate itin the 
moft economical manner. Oxymur acid 1s- 
capable of converting copper into a greeg 
oxides 
