MANUFACTURE OF ACETATE OF LEAD. 
259 
into a large pan to settle, which it speedily does ; the solution 
after setting is ladled into a pan (malleable iron,) which may be 
made of cast iron, 6 ft. long, and 4 ft. \>road. The solution is 
made to boil in this pan, and allowed to settle, it is then transfer- 
red into a large hemispherical pan, capable of holding 300 or 400 
gallons, when it is brought down to about crystallizing strength. 
When the solution has become dense enough to crystallize, about 
three times its bulk of water is run in upon it, whilst boiling, the 
solution being constantly stirred. By this treatment, a consider- 
able quantity of pyroligneous matters may be skimmed off as fast as 
they rise to the surface ; when they are removed, the evaporation 
goes on as before. If the solution be still too much colored, 
another dose of water must be given. A little practice soon en- 
ables us to know where the evaporation should be checked. The 
ordinary method is, to rinse a ladle (which is used to skim off the 
tar from the solution) through the liquid, and observe how many 
drops of solution fall from it before the solution takes a stringy 
appearance ; if only ten or twelve fall, then it is strong enough. 
The liquid is now ladled out into malleable iron pans, 5 ft. long 
by 3 ft. broad, and about six inches deep, the sides being bevelled, 
or sloping outwards, from below upwards, to crystallize. After be- 
coming sufficiently firm, the sugar of lead is taken out by inverting 
the pan on a cloth. The pots used in the above process are heat- 
ed only at the bottom. — A. P. Halliday. 
Manufacture of the White Acetate of Lead. — This is prepared 
by dissolving litharge in acetic acid ; the acetic acid is first 
placed in a vessel, and the litharge added by degrees, well stir- 
ring the mixture until the solution does but lightly redden the lit- 
mus paper ; a quantity of water, equal to about one half the acid 
employed, is then run into the lead solution; heat is then ap- 
plied, and the mixture slowly evaporated for about twelve hours, 
or until it has acquired a density of about 1.500. During evapo- 
ration any impurities which rise to the surface are skimmed off, 
and when the solution has acquired its proper density it is run off 
into the crystallizing pans. When the mass of crystals has become 
sufficiently hard to allow of its removal en masse from the crys- 
tallizers, it is drained and placed on wooden racks in the drying 
house, and when dry cleaned and broken up into fragments for 
the market. 
