DU.NGING. One of the processes of dyeing and calico printing. The steeping the goods in a bath of eowdung.
Experience has proved that clanging is one of the most important steps in the process of calico printing, and that if it be not well performed the dyeing is good for nothing. Before we can assign its peculiar function to the dung in this case, we must know its composition. Fresh cows' dung is commonly neutral when tested by litmus paper ; but some times it is slightly alkaline, owing, proba bly, to some peculiarity in the fobd of the animal.
The total constituents of 100 parts of cow dung are as follows: Water, 69.58; bitter matter, 0.74; sweet substance, 0.93 ; chlorophylle, 0.28 ; albumine, 0.63; miniate of soda, 0'08 ; sulphate of pot ash, 0•05• sulphate of lime, 0.25; car bonate of lime, 0.24; phosphate of lime, 0.46 ; carbonate of iron, 0.09 ; woody fibre, 26.39 ; silica, 1.14 • loss, 0-14. In clanging calicoes the excess of un combined mordant is in part attracted by the soluble matters of the cow's dung, and forms an insoluble precipitate, which has no affinity for the cloth, especially in presence of the insoluble part ofthe dung, which strongly attracts alumina. The
most important part which that insoluble matter plays, is to seize the excess of the mordants, in proportion as they are dis eolved by the water of the bath, and thus to render their reaction upon the cloth impossible. It is only in the deposite, therefore, that the matters carried off from the cloth by the dung are to be found.
M. Camille Kcechlin ascribes the action of cow dung chiefly to its albuminous constituents combining with the alumina and iron, of the acetates of these bases dissolved by the hot water of the bath. The acids consequently set free, soon be come evident by the test of litmus paper, after a few pieces are passed through, and require to be got rid of either by a fresh bath, or by adding chalk to the old one. The dung thus serves also to fix the bases on the cloth, when used in moderation. It exercises likewise a dis oxydating power on the iron mordant, and restores it to a state more fit to com bine with coloring matter.