So MINERAIOGICAL 
the phlogifficated alkali I ufe is fo well 
prepared, that pure marine acid poured 
upon it does not fliew the lead mark of 
blue during the firft 24 hours, it never- 
thelefs adds a portion of iron when ufed 
to precipitate iron diffolved in acids. 
On account of this circumffance, very 
great circumfpection is required, in de¬ 
termining the exaCt quantity of metal 
contained in a folution, and precipitated 
by phlogifficated alkali. 
I have found 100 parts of iron in a me¬ 
tallic ftate, diffolved in marine acid, and 
precipitated by pure fixed vegetable al¬ 
kali, after being edulcorated and heated, 
to give 140 parts of phlogifficated calx 
of iron attractable by the magnet: and 
the fame quantity of iron, precipitated by 
cryftallized "phlogifficated alkali, per¬ 
fectly well prepared, the blue precipi¬ 
tate being edulcorated and heated, to 
give 260 parts of phlogifficated calx of 
iron. The quantity of phlogifficated 
alkali required for precipitating thofe 
100 
