Giving a Crowfoot Colour to Paper Pulp.

Practical Magazine 19, 1876

(Chemistry applied to the Arts, Manufactures, &c.
Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)

The colour of the crowfoot is one of the most agreeable in paper manufacture, but it is also very difficult to obtain in all the richness and brilliancy of the flower's hue. As in the case of many other colours for paper, the operation requires to be divided into two parts.

With every 100 kilogrammes (220 lbs.) of dry pulp, the following process is observed: On the one hand, 12 kilogrammes (26½ lbs.) of acetate of lead are boiled separately in 36 litres (about 8 gallons) of water, and 4 kilogrammes (about 8¾ lbs.) of bichromate of potass in 20 litres (about 4½ gallons) of water on the other. When the salts are completely dissolved, the same quantity of cold water is added to each solution as was used before, it is stirred, and the solution of acetate of lead is poured into that of the bichromate, the whole being stirred as the mixing takes place. The mixture is used in two separate basins, or troughs, and produces the first colouring of the pulp.

Supposing, as is to be expected, a uniform tint has been obtained, 2 litres (about 3½ pints) of a yellow orange colour are added, which are prepared in the following manner: 25 litres (5½ gallons) of caustic soda lye, marking 20° Baumé, are taken, to which are added 10½ kilogrammes (23 lbs.) of acetate of lead, and 3½ kilogrammes (7½ lbs.) of bichromate of potass, mixed dry, the whole being boiled for half-an-hour. From this are taken the two litres mentioned above for the second colouring.

- La Gaceta Industrial, May 25, 1876.

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