Why is alkaline dye acidic?

The dyes such as "Dragon Purple Purple and acetic acid" used in high school biology experiments are alkaline dyes. "Is alkaline dyes alkaline (pH> 7)?

The above -mentioned alkaline dyeing fluid uses acetic acid when preparing. How can their pH be greater than 7? It will definitely be less than 7. So, what is the basis of dye classification? How to understand?

Acetate red chromosomal solution is a relatively common alkaline dye, which is commonly used for nuclear chromosomes and chromosome fixing and dyeing. When the plant cells are divided, the chromosomes are used for chromosome, and alkaline dyeing liquids are needed. At this time, you can use acetic acid red or dragon gangster purple dye solution. In the testing of pollen, you can use acetic acid ocean -to detect whether the pollen is in a single -core stage. Acetic acid red -staining liquid contains high concentrations and ocean reds. PH is acidic, which is a good nucleus and mitochondrial stains.

Classification basis

According to the chemical properties of dyes, it can be divided into alkaline dyes, acidic dyes and composite dyes. Alkaline dyes refer to the color of the cations after the dye molecular ionization, the cationic is colorless, and the cation can be combined with the dye target to make the target color. The acidic dye refers to the color of the anion after the dye molecular ionization, the cation is colorless, and the anion can be combined with the dyeing target to color the target. Composite dyes are made from acidic and alkaline dyes.

In order to facilitate memory, you can understand this way

The definition of alkaline (or acidic) dyeing agent is not determined by the pH value of the dye solution, but is determined by the charge brought by the color aid group in the dye substance.

The chromosomes with a positive charged group are alkaline dyeing agent (also known as yang ion dye).

The chromosomal group with negative charges is an acid dyeing agent (also known as anion dye).

As a dyeing agent, there must be two conditions

The first is color; the part that produces color is called the hair color group

The color of the dye and the affinity between it and the tissue are determined by the molecular structure of the dye itself. Some groups of molecular structures absorb some wavelength light, without absorbing the light of another wavelength, which makes people feel like this material "color", so these groups are called "hair color groups" Essence

The second is that there must be affinity between the tissue of the dyed, and the part of the affinity between the organization is called a color aid group

The existence of the color -assisted group enables the dye material ionization, enhances the polarity, promotes the effect of dyes and tissue, and has the effect of dyeing.

It can be understood to classify according to the dyeing object.

(1) Alkaline dye can dye acidic substances, because acidic substances can be used to get out of H+to make themselves negatively charged. The colored cations in the alkaline dyeing liquid and the acidic substances with negative charge are attracted. color.

(2) Acid dyes can dye alkaline substances, because alkaline substances can be divorced from OH-to make themselves positive charge, colorful anion in acid dyeing and acidic substances with positive charge, and firmly dye it firmly. Color.

If the dyeing target is protein, the choice of dye changes according to the change of the solution pH. Because protein contains amino and carboxyl groups, in the acid solution, when the pH value of the solution is less than the electrical point of the protein, the protein belts positively and is easily stained by acid dyes. In an alkaline solution, when the pH value of the solution is greater than the electrical point of the protein, the protein is negatively charged and is easily stained by alkaline dyes.