Remarks on Tests for Cobult. 308 
the mixture to heat with borax before the blowpipe; the 
colour of the globule will be olzve green, and not blue. 
A small hook of platina wire was used as the support in 
the above experiments, and is pees one of the best oe 
ports employed. 
The existence of cobalt in the ore sent to you may be 
readily ascertained in the following way, viz. roast the ore, 
to expel the arsenic; puta globule of the roasted ore into 
a watch glass, and cover it with nitric acid; evaporate to 
dryness, and repeat the operation to convert the iron into 
peroxide; on careful evaporation the second time, a por- 
tion of a peach-blossom coloured or pink coloured residuum 
will be noticed. This is principally nttrate of cobalt, and 
often forms a circle round the glass: it is deliquescent. 
Now, to a small hook of fine platina wire, attach a colour- 
less globule of glass of borax, and on fusing it with a small 
portion of the peach-blossom coloured residuum, the charac- 
teristic bfwe of cobalt appears. Again, fuse it with a portion of 
oxide of iron; the blue colour disappears, and the peculiar 
greenish hue, which is produced by the fusion of the ore 
itself with borax, is noticed. By the method described 
above, the cobalt existing in less than half a grain of the 
ore may be detected. 
When the crystals of this arsenical cobalt (for I suppose 
we are entitled to call it so now, evenif it contains 74 per 100 
of iron,) are digested in dilute nitric acid, the solution, when 
concentrated, is of arose colour; and the decisive test* which 
you have recommended, had been tried with all possible 
success; the green sympathetic ink is formed, by the addi- 
tion of a solution of common salt tothe nitric solution of 
the crystals. 
It is evident that too great reliance has been placed on 
the appearance of the globule of borax, when a doubt has 
existed respecting the presence of cobalt; perhaps many 
crystals now called “ arsENIcAL iron,” from the results of 
fusion with borax, will be found, on farther examination, to 
contain cobalt ; and this eabaianee may be found to be more 
widely distributed, than it is now supposed to be. Perhaps 
there is no better or easier method of examination, than that 
* Viz. the formation of the green sympathetic ink, 
