64 MINERAL OG I CAL 
red colour, and afforded a green fym- 
pathetic ink, by adding fome portion 
of common fait; a proof that it contained 
ftill much iron. After having diluted it 
with water, I added flowly fixed vege¬ 
table alkali in folution, and took care 
to flop when the precipitate began to 
change its colour from that of a muddy 
calx of iron to a violet, and the folution 
had obtained a clear rofe colour. This 
folution freed from all precipitate of 
iron by the filtre, and employed as a 
iympathetic ink, gave a beautiful fky- 
blue. It was now completely faturated 
with alkali, and the pure calx of cobalt 
was precipitated of a violet colour, and 
when edulcorated, dried, and finely le¬ 
vigated, weighed 70 grains. Two grains 
of it mixed with one ounce of glafs 
frit, gave, when properly melted, a very 
fine fapphire blue glafs. 
(c) The iron which had been united 
with the regulus of cobalt, and which 
was precipitated from the folution in 
nitrous 
