8 2 Mr . kir wan’s- Experiments and Obfervations on 
tlie cobalt, afterwards re-takes it, and lets fall the dephlogiilr- 
cate'd calx of iron. 
Nickel alio, though it does not precipitate cobalt itfelf, as- 
appears by the remaining rednefs of the folution, yet conftantly 
precipitates fome other heterogenous fubftance from it. The 
folution of cobalt in the marine acid becomes colourlefs by the 
addition of nickel. 
Wifmuth is foluble in the vitriolic and nitrous folutions of 
cobalt, and caufes a fniall white precipitate, but does not affett 
the true cobaltic part. Thefe folutions in vitriolic acid cannot 
be attributed to an excefs of acid, as they are made in a dilute 
acid, and without heat. Copper alfo precipitates a white fub- 
fiance from the nitrous folution of cobalt, which I take to be 
arfenic. 
It is difficult to procure either nickel or cobalt very pure ; it 
is evident thofe I ufed were not fo. 
Of precipitations of and by regulus of antimony. 
Copper neither precipitates, nor is precipitated from, the 
vitriolic acid by regulus of antimony, at leaf! in three days y 
but vitriol of antimony in fpeeie diffolves it (lowly. 
The regulus is alfo afted upon by vitriol of lead, for it be- 
comes red after remaining 16 hours in the folution of that vi- 
triol; and lead fcarcely precipitates it from the vitriolic acid. 
I alfo found, that powdered regulus precipitates vitriol of 
mercury very (lightly. 
Wifmuth neither precipitates, nor is precipitated by, this 
regulus from the vitriolic acid in 24 hours. 
Though tin precipitates this regulus from the nitrous acid, 
yet if the regulus be put into a folution of tin in this acid, in 
16 hours neither will be found in the folution, either 
by 
