c. There are numerous ways of folding filter paper. The most commonly used
folds are the "plain filter," made from the circular filter paper sheet by two simple folds,
and the "pharmaceutical" or "plaited" filter. To prepare a "plaited" filter, start by folding
the circular paper into quarter sections. At the beginning of a quarter section, make
folds of approximately one-half inch in alternating directions until the quarter section is
completely folded. Fold the remaining quarter sections in the same manner. The
creases must NOT be too sharp; otherwise, the fibers will be loosened. Furthermore,
the creases must NOT go all the way to the center because this will seriously weaken
the filter.
d. Prior to filtering and solution, the filter paper (no matter what the fold) should
be wetted with sterile water. See figure 1-7, which illustrates the two methods of folding
filter paper.
1-16. COLATION
Colation, or straining, is essentially the same process as filtration.
The difference between collation and filtration is the particle size to be separated and
consequently the nature of the intervening media. The process of collation separates a
coarser solid from a liquid by passing the mixture through a cloth, gauze, or long-fibered
cotton. Collation is more realistic than filtration for removing foreign particles from
syrups and other slow-flowing liquids.
MD0809
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