644 EXPERIMENTAL INVESTIGATION OF THE 
thus to arrive at the conclusion that pure bismuth 
is not susceptible of any direct magnetic action 
by the mere approach of the poles of a powerful 
magnet, which I consider a test of far greater 
certainty and exactness than that of a feeble 
magnetic needle, whatever may be the delicacy of 
its suspension ; and as a peculiar class of pheno- 
mena become displayed by a sudden develope- 
ment of the powers of an electro-magnet, much 
misconception might rise from its employment. 
22. The most usual impurities of bismuth of 
commerce are sulphur and arsenic, and, occasion- 
ally, a small portion of silver and iron. On sub- 
jecting the drossy part (19) to dilute sulphuric 
acid a portion was dissolved ; after which the liquid 
was reduced almost to dryness by evaporation. 
The residue being diluted with water, and a solu- 
tion of ferrocyanuret of potassium being added, 
it assumed a blue colour, which indicated that 
a portion of iron had been dissolved from the 
mass. On dissolving another portion of the dross 
(19) in dilute sulphuric acid, the presence of iron 
was again indicated by the addition of bruised 
gall nut. Hence it was fair to infer that the 
whole of the magnetic action displayed by the 
mass was due to the iron it contained. 
