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White Lead {Lead. / Sulphide of Lead (Black.)

{Carbonic Acid.



Such is the theory of the reaction which might take place, but which, as

far as our own experience goes, does not. Some deep cadmium yellow which

we ourselves prepared was intimately mixed and ground with an equal

quantity by weight of Cremnitz white, and an oil rub of the compound

laid upon a tile. Having placed the latter on a shelf in the laboratory,

we watched from week to week to see if any approach to blackness

occurred, any diminution in the beauty of the tint; but could perceive

none. Hence, while admitting the possibility of the colour being

damaged or destroyed in the case of an inferior and spurious article, we

conclude that an unadulterated cadmium yellow, containing no free

sulphur, neither injures, nor is injured by, white lead, and may safely

be used therewith. At the same time, the artist should be warned to

satisfy himself of the genuineness of his pigment, or otherwise to

employ the white of zinc, at least as a medium of intervention.



A good sample of cadmium yellow may rather advantageously than otherwise

be compounded with white lead, for we have found that a mixture of equal

parts by weight of the two will bear an atmosphere of sulphuretted

hydrogen that completely blackens the white alone.



With all the sulphides of cadmium a steel palette knife is best avoided.



TTITLE PALE CADMIUM.



The cadmium yellow so-called, is not strictly pale, but pale only when

compared with the preceding. It is, in fact, a full rich colour,

brilliant and permanent, but without that tendency to orange which

distinguishes the deep. For some purposes, when a warm tone is not

required, such a tint is preferable. In water, especially, where

delicacy of colouring can be carried to a greater degree of refinement

than in oil, these differences of hue are important. In the first

medium the faint washes show with a clearness which is not so apparent

in the last, and the most subtle gradation of tone tells with a force in

some measure lost in oil. As a consequence, the colour of the lightest

tints in the distance must be as true as that of the deepest shades in

the foreground, and hence the warmth or coldness of the pale washes of a

pigment should be duly considered.



Pale cadmium yellow with or without aureolin, is adapted for golden

sunsets, and yields with French blue a beautiful sea-green.



TTITLE LEMON CADMIUM.



Very pale cadmium yellows are not permanent, and lemon cadmiums are

decidedly fugitive. Being, like the deep and 'pale' varieties,

sulphides, they are of course unaltered by sulphurous gas; but they will

not stand exposure to light and air, or even to light alone. Some which

were submitted in an air-tight bottle to the action of light gradually

whitened next the glass. Yet they were almost identical in composition

with the deepest and most orange hues, and might have reasonably been

presumed stable. Repeated experiments, however, both with samples of our

own making and of others' manufacture, have shown that for a cadmium to

be durable, it must be of a full, rich, comparatively deep yellow; and

that any paler product than the 'pale' alluded to cannot be depended

on. It is true that a light or lemon tint will fade quicker in water

than in oil, but a colour which is fugitive in the one vehicle cannot be

regarded as eligible in the other. From a somewhat long acquaintance

with cadmiums, we have derived the opinion that their stability rests

much on the mode of preparation, and that an amount of heat is needed





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