459 
Prussian Blue. 
ever. The produce in the hogshead will be fetid oil, 
and volatile alkaline liquor. The residue in the retort is 
taken out, and broken to pieces. It is then put into an 
iron pot set in brick work and mixed well with three times 
its weight of potash. They operate commonly upon 
lOlbs. of the coaly matter, and 30ibs. of fixed alkali. The 
pot is heated gradually for an hour ; then the heat is rais- 
ed till the contents are fused. This operation lasts 12 
hours, the matter is kept stirred all the time with an iron 
rod, when the matter thus fused gives out a smell of liver 
of sulphur, it is drawn red hot from the pot, thrown into 
water and boiled therein for half an hour. It is then pour- 
ed off and fresh water boiled upon it to extract all the ley, 
which is filtered through cloth. Four parts of alum and 
one of green vitriol are then dissolved together and filter* 
ed. This is precipitated by the ley, and the precipitate 
left to dry. 
Some manufacturers proceed thus. Take 6lbs. par- 
ings of skins , as much hoof and horns cut small : add JLOlbs. 
potash : put them in an iron pot : let them macerate co- 
vered with water for 8 days, evaporate the water : put the 
mixture in a large iron pot, in which you have previously 
dissolved 21bs. of crude tartar. Continue the fire till the 
substances are perfectly calcined : lixiviate. Then dis* 
solve 51bs. green vitriol and ISIbs. of alum water, and 
put this solution and the ley together. 
The objection I have to the above recipes, is that the 
quantity of alkali is too much for the animal matter, 
and the alum and copperas also in too great proportion 
but they bear the stamp of actual processes. M. Bau- 
nach’s method of saving the volatile alkali seems to be 
economical, but I doubt whether there be not a loss of 
prussic acid. 
The cheapness of hoofs, horns, and leather clippings 
In Philadelphia, makes this manufacture a desirable one 
