Behavior in Solution
| Congo red (pH indicator) | ||
| below pH 3.0 | above pH 5.2 | |
| 3.0 | ↔ | 5.2 |
Due to a color change from blue to red at pH 3.0-5.2, congo red can be used as a pH indicator. Since this color change is an approximate inverse of that of litmus, it can be used with litmus paper in a simple parlor trick: add a drop or two of congo red to both an acid solution and a base solution. Dipping red litmus paper in the red solution will turn it blue, while dipping blue litmus paper in the blue solution will turn it red.
Congo red has a propensity to aggregate in aqueous and organic solutions. The proposed mechanisms suggest hydrophobic interactions between the aromatic rings of the dye molecules, leading to a pi-pi stacking phenomenon. Although these aggregates are present under various sizes and shapes, the "ribbon-like micelles" of a few molecules seem to be the predominant form (even if the "micelle" term is not totally appropriate here). This aggregation phenomenon is more prevalent in high congo red concentrations, at high salinity and/or low pH.
Read more about this topic: Congo Red
Famous quotes containing the words behavior in, behavior and/or solution:
“The inability to control our children’s behavior feels the same as not being able to control it in ourselves. And the fact is that primitive behavior in children does unleash primitive behavior in mothers. That’s what frightens mothers most. For young children, even when out of control, do not have the power to destroy their mothers, but mothers who are out of control feel that they may destroy their children.”
—Elaine Heffner (20th century)
“Reading about ethics is about as likely to improve one’s behavior as reading about sports is to make one into an athlete.”
—Mason Cooley (b. 1927)
“There’s one solution that ends all life’s problems.”
—Chinese proverb.