144 Mr. Kirwan’s Experiments 
Nitrous folution of zinc , thus treated, (hews a dirty white ; 
a that of bifmuth a brown mixed with white ; and that of cobalt 
a brown and black precipitate. 
As PruJJian alkali always contains fome iron, it gives a pur- 
ple precipitate with this teft, which precipitate is eafily dif- 
folved. 
It turns tin&ure of raddifhes, which is my teft for alkalies* 
green. 
The action of liver of fulphur on metallic fubftances in the 
dry way is defcribed by many authors, and particularly in an 
excellent Diflertation by M. Engestrom ; but its aftion in 
the moifl way has not been mentioned, as far as I recolledt, by 
any. Hence I tried its effect on a few grains of iron, cop- 
per, lead, tin, zinc, bifmuth, regulus of antimony, and 
of arfenic. Putting each into a bottle, containing about three 
half ounces of liquid liver of fulphur, fo far diluted that its 
colour was yellow ; in about fifteen days I found they all, 
except the zinc and tin, had attra&ed fulphur from the fixed 
alkali. Iron, arfenic, and regulus of antimony and lead, were 
moft altered ; copper next, and bifmuth leaft : but the liquors 
held none of the metals in folution ; that which contained iron 
became green ; on adding an acid fulphur was precipitated ; if 
it held iron it could not at that period be dete&ed. 
Water faturated with the condenfed refiduum of alkaline and 
hepatic air, that is, with the pureft volatile liver of fulphur, 
does not precipitate marine Jelenite , though it forms a flight 
brown and white cloud in that of marine baro-felenite. 
It produces a black precipitate in the folution of vitriol of 
iron , and a black and white in that of marine fait of iron ; but 
by agitation this laft becomes wholly white. 
It 
