When we do biomedical experiments or some physical chemistry experiments, in order to better observe the experimental results, usually choose a reasonable dye, after selecting the appropriate dye, we can observe the expected experimental phenomena or results. The dyeing agent can be divided into natural dyes and synthetic dyes according to the source, and different kinds of dyeing agents can be selected in different experiments.
The high school biology textbook describes chromatin as saying: chromatin (body) is easily dyed by alkaline dyes to be dark. In the experiment, staining of chromatin (body) should be done by using Gentian solution or alkaline stain such as magenta solution, which was prepared by dissolving in acetic acid solution of gentian or magenta, and the ph value of gentian solution was less than 7 (acidic). So why is the Gentian solution called an alkaline stain?
One is the color, and the other is to have affinity with the dyed tissue. The color of dyes and the affinity between it and the tissue are determined by the molecular structure of the dye itself, and the color-producing chromophores clusters and the chromophores groups that produce affinity with the tissues determine the dyeing properties of the dye. As a dye substance, in addition to having a chromophores group, there is also a need for a chromophores group to enable the ionization of compounds to occur. such as dye compounds often by nitro (-no2), Azo (-n=n-), vinyl and other formation of the Chromophores group, and by Oh,-SO3H,-and other acidic groups and-,-NHCH3,-N (CH3) 2 and other alkaline groups to form a chromophores group. Their presence makes the dye matter ionic, polarity enhancement, promote the interaction between dye and tissue, produce dyeing effect. We have a chromophores group of dyes with acidic or alkaline groups known as acidic or alkaline staining agents.
If Nitro is a chromophores group, when 3 hydrogen atoms in the benzene ring are replaced by 3 Nitro, they become the yellow compound of nitrobenzene. Nitrobenzene is not a dye, only a hair chromophores regiment, it does not dissolve in water, also can not be ionized, neither acid nor alkali, can not be with acid or alkali formation salts. If the three nitrobenzene molecule, replace a hydrogen atom with hydroxyl, it becomes the nitrophenol, namely Picric, it is a kind of yellow dye, have ionization function, and strong alkali can form salt, here hydroxyl is to help chromophores Regiment. It can be found that the color of bitter acid is caused by the Chromophores Group (Nitro), and its dyeing performance is the help of chromophores Group (hydroxyl) formation, such as the use of amino instead of Nitro, the formation of colorless compounds, not dyes. Thus, as a dye, it is necessary to have a chromophores regiment and help the Chromophores Regiment to cooperate with each other.
If Eosin y contains a (-) Chromophores group that emits hydrogen ions when ionized in water, it is negatively charged. The preparation of red y dye, and alkali NaOH action to generate salt (-coona), the substance of the + instead in the solution is alkaline, it is not possible to think that acidic dyes in the solution is acidic.
A fixture to be prepared when clothing is dyed:
Fixture must have acid and alkali resistance, corrosion-resistant, no metal, no rust characteristics. The market clips are not suitable as clothing dyeing fixture, because the spring metal ring with acid-base chemicals contact easy to rust, resulting in contaminated clothing, resulting in difficult to clean rust stains. The best use of all plastic pp materials (including springs), this material will not and stained water produced chemical reaction, is suitable for garment dyeing industry. This whole plastic clip on Taobao on the Xinyuan plastic can be bought.
Therefore, the definition of acidic (alkaline) stain is not determined by the ph value of the dye solution, but is determined by the charge charged by the Chromophores group after it is ionized in the dye material. In general, the Chromophores group with positive charge of the dye is alkaline stain, on the contrary, acidic staining agent.