Mr J. F. W. Herschel on the 
298 
object in analysis. The principle here developed furnishes 
a ready method of detecting the minutest quantities of other 
metals in union with iron, and therefore cannot but prove of 
important service in various cases where this metal consti- 
tutes the chief ingredient in the substance examined, as in 
meteoric iron, the various natural oxides of this metal, &c. &c. 
I will exemplify this in one or two instances. 
36*00 grains of meteoric iron (furnished me by the kind- 
ness of Dr. Wollaston) were dissolved in dilute nitro- 
sulphuric acid, leaving behind a minute quantity of a brilliant 
black powder, which however dissolved by digestion in nitro- 
muriatic acid, and appeared only to contain an excess of nickel. 
The solutions were mixed, and being neutralized at a boiling 
temperature by carbonate of ammonia, and the iron separated, 
a green solution remained. Into this when boiling, a drop of 
persulphate of iron being let fall, was immediately precipi- 
tated in the state of subsulphate, which being separated, the 
solution was boiled with excess of caustic potash till all smell 
of ammonia disappeared. Oxide of nickel separated, which 
collected and strongly ignited, weighed 4*65 grains, or 12*92 
on the hundred, which (taking the atom of nickel to weigh 
30, and that of oxygen 8, hydrogen being unity) gives 10*20 
per cent for the contents of the specimen analyzed in metallic 
nickel. 
100 grains of titanious iron from North America, being 
dissolved in muriatic acid (after the requisite ignition with 
potash) were treated (after separating the titanium) with 
excess of carbonate of lime and filtered. The excess of car- 
bonic acid being expelled, ammonia was added, and a small 
quantity of a white precipitate fell, which speedily blackened 
