458 Prussian Blue . 
much dependant on the degree of heat employed, the 
matter begins to make a considerable hissing noise, it is 
then to be constantly stirred until it becomes fused, then 
take it out of the calciner with an iron ladle and put it in- 
to any convenient iron vessel to cool. If the process has 
been properly conducted, it will appear in a cake of a 
dark dull green, the texture of which is much like liver 
of sulphur, Hepar sulphuris. This mass is to be broken 
in pieces, thrown into water and left in a covered vessel for 
two days to dissolve, 45 lbs. of alum and 15 lbs. of green 
copperas are dissolved in boiling water and left to set- 
tle. The clear liquor is decanted and made boiling 
hot, and the lixivium is likewise to be decanted and rni xt 
with the other solution by putting alternately four parts 
of the alum and copperas liquor, to one part of the lix- 
ivium. The mixture is to be well stirred on each ad- 
dition as an effervescence will take place, which without 
that caution would be likely to rise over the sides of the 
vessel. The prussian blue precipitates of a dark dull 
green, the liquor is then to be drawn off as close as possi- 
ble, and more clean water added : the ablutions are to 
be repeated till the precipitate puts on the appearance of 
a very fine blue and is thoroughly edulcorated, which 
generally takes sixteen washings ; it is then to be put on 
fibres, and afterwards to be dried on chalk stones. 
(I have not noted my authority for the above receipt, 
but I believe it is from the relation of a manufacturer.) 
Method of making prussian blue in Germany , by M. 
BaunachyJour.de Bos . 1778, part 1 , p. 312. 
Take the horns and hoofs, of animals, the waste cuttings 
©f leather, the latter in equal quantity with the former. Re- 
duce them to small pieces, put them in a tubulated iron 
retort, and set this in a reverberatory furnace. Adopt a 
hogshead as a receiver : distill while any tiling comes 
