It is used as a pigment (cadmium yellow), for it retains its colour in an atmosphere containing sulphuretted hydrogen; it melts at a white heat, and on cooling solidifies to a lemon-yellow micaceous mass.
It may be generally inferred that an increase in molecular weight is accompanied by a change in colour in the direction of the violet.
A theory of colour in opposition to the Witt theory was proposed by Henry Armstrong in 1888 and 1892.
From the greater value of the fur, silver greys have been frequently employed to stock warrens, as they breed true to colour in the open if the ordinary wild rabbits are excluded.
At the same time there is often a change in colour in the flowers, which are red in bud, becoming blue as they expand, as in Myosotis, Echium, Symphytum and others.
