RED MINERAL PIGMENTS.

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water-bath to about 45 0 C. After some hours the mixture acquires a scarletcolour, and is then colle< 5 ted on filters, washed, and dried. The dried powderis the vermillion of commerce.

The annexed specimen of vermillion-red we owe to the kindness of Mr,Walter Crum, of the Thorniebank Print Works, Glasgow. It is produced by thefollowing process :—5 lbs. of vermillion are mixed with 1 gallon of thickening;the colour is then printed on the fabric, which is dried and steamed for onehour. The thickening consists of a mixture of solutions of gum-dragon andegg-albumen. These may be in different proportions, according to the degree offastness required. The more albumen used the faster will be any pigment orpaint colour. The gum-dragon solution is used in the proportion of | to | lb.per gallon of colour, and the albumen to the amount of 4 lbs. in the gallon ofcolour: these proportions yield the fastest colour that is prepared. 2 lbs. ofalbumen will give a moderately fast colour.

Vermillion Red.

Oxysulphuret of antimony, antimony cinnabar, or antimony vermillion, is asimilar compound to vermillion. It may be prepared on the large scale by thefollowing process:—Black sulphuret of antimony is calcined in a current ofair and steam, with the view of forming antimonic oxide and sulphurous acid,the latter being employed for the preparation of dithionite of calcium fromsoda-waste. The antimonic oxide is dissolved in hydrochloric acid. Largewooden vessels, heated by steam-pipes, are nearly filled with a solution ofdithionite of calcium, and the protochloride of antimony is added gradually,the liquid being stirred and heated to about 6o° C. After the reaction hasceased and the precipitate subsided, the latter is washed and dried at a tem-perature under 50° C. Mixed with water or a solution of gum, the colourappears very dull; but as an oil-colour it possesses the most intense brilliancy.Recipes for its application to printing have not been given.

Of the other red pigments, of very limited application in printing, we neednot speak in detail.