FIL′TERING POWDERS

Prep. 1. Fuller’s earth washed, dried without heat, and reduced to coarse powder. 2. Pipe clay or potter’s clay, as the last. Both the above are used to filter and bleach oils. 3. Clay or fuller’s earth, 1 part; fine siliceous sand, 2 parts; the two are separately washed, after which they are drained, and mixed together, and dried as before. Used for GLUTINOUS OILS . 4. Granulated animal charcoal, sifted and fanned from the dust. Used to filter and bleach SYRUPS and VEGETABLE SOLUTIONS . Obs. Filtering powders are prepared of several degrees of coarsene , and should be chosen with reference to the degree of fluidity of the liquid to be filtered through them. In no case should they be reduced to fine powder, as not only is the proce of filtration thereby rendered unnece arily tedious, but in some cases (as when charcoal dust is mixed with glutinous vegetable solutions and syrups) the filtrate carries off a portion of the powder, which can afterwards be separated from it only with considerable difficulty. See Charcoal , Filtration , Oil , .