or Marrone Lake, was a preparation of madder, of great depth, transparency, and stability. Working well in water, glazing and drying in oil, and in every respect a good pigment, it was one of those colours which gradually--and often, as in this case, unfortunately--become obsolete, on account of their hues being easily given by admixture of other pigments. There was likewise a deeper kind, called Purple Black. A good madder marrone may be produced by adding to brown madder either rose madder, madder carmine, or Rubens' madder, with a slight portion of black or blue if required. 282. _Mars Marrone._ Under the heading of a New Marrone Pigment there appeared some months back in a chemical journal the following:--"The blood-red compound obtained by adding a soluble sulphocyanide to a salt of iron in solution can be made (apparently at least) to combine with resin thus: To a concentrated solution of sesquichloride of iron and sulphocyanide of potassium in ether, an etherial solution of common resin is added, and the whole well shaken together. There is then mixed with it a sufficiency of water to cause a precipitate, when it will be found, after the mixture has stood a few hours, that the whole or nearly the whole of the red-coloured iron compound has united with the precipitated resin, forming the marrone-coloured pigment in question. When this coloured substance is finely powdered and mixed with water, the liquid is not the least coloured; whence it is inferred that the red iron compound has chemically united itself with the resin." The foregoing account is rather to be regarded as of scientific interest than of practical utility. The blood-red solution of sulphocyanide of iron is in itself not stable: when the red solution of this salt is so exposed to the sun, that the rays pass through the glass jar containing it, it is rendered colourless, but the colour is retained or restored when the rays pass directly from the air into the fluid; so that when a properly diluted solution is placed in a cylindrical glass vessel in direct sunshine, it loses colour in the morning till about eleven in the forenoon, when the rays beginning to fall upon the surface exposed to the air, gradually restore the colour, which attains its maximum about two o'clock. Moreover, the solution is immediately decolourised by sulphuretted hydrogen and other deoxidizing agents, as well as by alkalies and many acids. It is scarcely probable that the union of the red colouring matter with the resin would suffice to secure it from change; and there is little doubt that the new marrone pigment would be a chameleon colour. * * * * *