Introduction of Common Artificial Dyes

Artificial dyes include aniline dyes or coal tar dyes, which are widely used in a wide variety of applications. The disadvantage of artificial dyes is that they are easily faded after exposure to sunlight, and aniline blue, bright green, and methyl green are more likely to fade. However, if you pay attention to the pH in production and avoid direct sunlight, artificial dyes will not fade after several years. Some common artificial dyes are listed as below:



Acidic magenta is an acid dye that is red powder, soluble in water and slightly soluble in alcohol (0.3%). It is a good cell staining agent and it can also be used on plant-made tablets to stain parenchyma, pith and other parenchyma cells and cellulosic walls. Tissue sections should be immersed in acidic water prior to staining to enhance its staining power. Acidic fuchsin is easy to react with alkali, causing excessive dyeing and fading in tap water.



Congo red is an acid dye that is jujube red powder, soluble in water and alcohol, and appears blue in acid. It can be used as a dye and as an indicator. It is often used as a liner agent for hematoxylin or other cellular dyes in plant. When congo red is used to stain the cytoplasm, it can dye the gum or cellulose red. It can used in animal tissue preparation to dye nerve axes, elastic fibers, embryo materials, and so on. Congo red can be double-stained with hematoxylin. Since it is soluble in water and alcohol, it needs to be completed quickly during washing and dehydration.



Methyl blue is a weak acid dye that is soluble in water and alcohol. It can be used with eosin to dye nerve cells, and it is also an indispensable dye in bacterial preparation. Its aqueous solution is vital dye for protozoa. Methyl blue is extremely oxidizable, so the color dyed with it cannot be maintained for a long time.



Fastgreen is an acid dye that is soluble in water (solubility is 4%) and alcohol (solubility is 9%). Fastgreen is a staining agent for the dyeing of cellulose cell tissue containing pulp. It is widely used in the dyeing of cells and plant tissues. Fastgreen, hematoxylin and fragrant red are listed as the three most commonly used dyes in plant histology.



Aniline blue is a mixed acid dye. This dye is generally difficult to dissolve in water and is not readily soluble in alcohol (1.5%). It can be used in plant preparations with saffron for tissue staining and it can also be used to dye algae plants. Because the composition of this dye is very inconsistent, the dyeing effect is not clear as well


Sudan Ⅲ

Sudan III is a weak acidic dye and is red powder that does not dissolve in water. It is easily soluble in fats and alcohols (solubility is 0.15%). Sudan III is a coloring agent for fat.


Sudan Ⅳ

Sudan IV is a weak acid dye, which is also a good dye for fat. Nowadays, Sudan IV is used to replace Sudan III It can dye resin, milk tube, wax and keratin. It can also make the chloroplast dyed dark red.



There are many types of such dyes. The commonly used Eosin Y is an acid dye which is red and blue small crystal or brown powder, soluble in water and alcohol (solubility is 2% when soluble in anhydrous alcohol). Eosin has a wide range of applications in animal production. It is a good cytoplasmic dye and is often used as a lining agent for hematoxylin.



Basic fuchsin is a basic dye that is dark red powder or crystal and soluble in water (solubility is 1%) and alcohol (solubility is 8%). Basic fuchsin is widely used in biological preparations and can be used to dye collagen fibers, elastic fibers, nucleus of rediscus particles and central nervous tissues, lignified wall of vascular plants, prototheca, and algae. In bacteriological preparations, basic fuchsin is commonly used to identify Mycobacterium tuberculosis.



Crystal violet is a basic dye that is soluble in water (solubility is 9%) and alcohol (solubility is 8.75%). Crystal violet is an excellent stain, which is widely used in cytology, histology and bacteriology. It is often used as a nuclear stain for displaying the centrosome of a chromosome, and can dye the starch, fibrin and glia. The disadvantage of slice dyed with crystal violet is that it is not easy to preserve for a long time.



Gentian violet is a mixed basic dye, mainly a mixture of crystal violet and methyl violet. When necessary, gentian violet can be used interchangeably with crystal violet. The main ingredient of the gentian violet used in medicine is methyl violet.



Neutral red is a weak basic dye that is red powder and soluble in water (solubility is 4%) and alcohol (solubility is 1.8%). It appears yellow in alkaline solution, appears blue in strongly alkaline solution, and appears red in weak acidic solution, so it can be used as an indicator. Neutral red is non-toxic and is often used as a vital dye, which is used to dye protozoa and display the contents of living cells in animal and plant tissues.



Safranin is a basic dye that is soluble in water and alcohol. Safranin is a commonly used dye in the field of cytology and histology of animals and plants. It can stain the nucleus, chromosomes, plant proteins and sporangia.



Methylene blue is a basic dye which is blue powder and soluble in water (solubility is 9.5%) and alcohol (solubility is 6%). Methylene blue is a very important dye for the dyeing of nuclear, which has the advantage that the dyed color will not be too deep.



Methyl green is a basic dye. It is green powder and soluble in water (solubility is 8%) and alcohol (solubility is 3%). Methyl green is the most valuable stain for the dyeing of cells, which is commonly used in cell research to stain chromatin and can also be used to dye the xylem of plants.

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