Iodine Blue
:
ON THE PRIMARY, BLUE.
It is curious that iodine, which gives a yellow with lead, should also
afford a blue with the same metal. When a solution of iodine in aqueous
soda (carbonate of soda is not so good) is added to nitrate or acetate
of lead-oxide, a transient violet-red precipitate falls, which
decomposes spontaneously under water, yielding iodine and a beautiful
blue powder. The colour, however, is exceedingly fugitive, even the
carbonic acid of the air separating iodine from it and forming a lead
salt. Bearing in mind the scarlet iodide of mercury, iodine is capable
of furnishing the three primary colours, distinguished alike by their
brilliancy and fugacity.