To perform a simple paper chromatography experiment to separate the pigments in black ink, scientists follow a precise sequence of steps. First, a thin line is drawn with a pencil about two centimeters from the bottom edge of a strip of chromatography paper. Next, a small dot of the black ink to be analyzed is placed directly on the center of this pencil line and allowed to dry completely. After the ink dries, the paper strip is suspended vertically inside a beaker containing a small amount of solvent, such as rubbing alcohol. It is crucial that the solvent level is low enough so that it does not submerge the ink dot itself. As the solvent rises up the paper through capillary action, it carries the ink pigments with it at different rates. Once the solvent front reaches near the top of the paper, the strip is removed from the beaker and laid flat to dry before the separated color bands are measured and recorded.
According to the procedure described in the passage, what must happen to the black ink dot before the chromatography paper strip is suspended inside the beaker?
- It must be allowed to dry completely on the paper.Answer
- BIt must be submerged directly in the solvent.
- CIt must be measured and its color bands recorded.
- DIt must be covered with a second pencil line.