Dyes and Pigments in Chemistry

Sedatives are used for mentally agitated or violent patients. Equanil (chemical name - meprobanate) and calmpose (diazepam) are a couple of common drugs in this category.

Information pheromones are indicative of an animal's identity or territory. For example, dogs and cats deposit chemicals in and around their territory, which then serve as an indicator for other members of the species about the presence of the occupant in that territory.

Optical brighteners, are dyes that absorb light in the ultraviolet and violet region (usually 340-370 nm) of the electromagnetic spectrum, and re-emit light in the blue region (typically 420-470 nm). Fluorescent activity is a short term or rapid emission response, unlike phosphorescence, which is a delayed emission.

The phthalocyanine dyes are few in number, but  are commonly used. Alcian blue is employed in one of the standard methods for acid mucopolysaccharides. Luxol fast blue is used to demonstrate myelin.

Tetracyclines (Chloro and oxy) are broad spectrum antibiotics (antibiotics capable of curing many infections) and cure diseases caused by many bacteria, large viruses, protozoa, parasites and rickettsiae. These can be orally administered since they are absorbed from the gastro intestinal tract.

Colouring materials have been used for many thousands of years by man. The two old ways were to cover with a pigment (painting), or to colour the whole mass (dyeing). Pigments for painting were usually made from ground up coloured rocks and minerals, and the dyes were obtained from animals and plants. However, some of our most common dyes are still derived from natural sources. These are termed natural dyes.

Amphoteric dyes have both positively chargeable groups and negatively chargeable groups present on the molecule. Depending on the charge actually present, these dyes may interact as either positively charged ions (basic dyes) or negatively charged ions (acid dyes) e.g. ,celestine blue B .

The first human-made (synthetic) organic dye, mauveine, was discovered serendipitously by William Henry Perkin in 1856. Many thousands of synthetic dyes have since been prepared.

Xanthene dyes are the group of brilliant fluorescent yellow to pink to bluish red dyes characterized by the presence of the xanthene nucleus, known sometimes in colourless as well as coloured forms, and used chiefly in dyeing textile fibres, in colouring paper, in producing fluorescent effects and as organic pigments.

Releaser pheromones are pheromones that cause an alteration in the behaviour of the recipient. For example, some organisms use powerful attractant molecules to attract mates from a distance of two miles or more. In general, this type of pheromone elicits a rapid response, but is quickly degraded.

Arylmethane dyes are so called because they are derived from methane, in which some of the hydrogen atoms are replaced with aryl rings. Since a synonym for aryl is phenyl, they may also legitimately be called phenylmethane dyes. Aryl rings are often referred to as benzene rings. However, benzene is a specific chemical compound and this usage is technically incorrect, although very common.

Acridine orange is a nucleic acid selective fluorescent cationic dye useful for cell cycle determination. It is cell-permeable, and interacts with DNA and RNA by intercalation or electrostatic attractions.

The purpurin, is a naturally occurring red/yellow dye. It is an organic compound formally derived from anthraquinone by replacement of three hydrogen atoms by hydroxyl (OH) groups. Purpurin is also called verantin. It is a minor component of the classical lake pigment madder lake or Rose Madder.

Quinizarin is an orange or red-brown crystalline powder. It is formally derived from anthraquinone by replacement of two hydrogen atoms by hydroxyl (OH) groups. It is one of ten dihydroxyanthraquinone isomers and occurs in small amounts (as a glycoside) in the root of the madder plant, Rubia tinctorum.

Sudan Blue II is used as a dye for alcoholic, ester, and hydrocarbon based solvents, oils, fats, and waxes. It is used also in lacquers and inks. In some countries, it is used as a fuel dye. It is also used in some blue coloured smoke formulations. In microscopy, it is used as a staining dye.

Aurintricarboxylic acid (ATA) is a form of dye that is used to inhibit protein biosynthesis in its initial stages. Nominally, it is used in biological experiments as a protein inhibitor, and as an ammonium salt (known as aluminon) it is used as a reagent to estimate  aluminium in water, biological tissue and foods.

Morindone is an anthraquinone compound obtained from various Morinda species, especially M. tinctoria, and also M. citrifolia. Its principal use is as a dye, but it has also been investigated for anticancer and microbial uses.

Bromothymol blue is a chemical indicator for weak acids and bases. The chemical is also used for observing photosynthetic activities or respiratory indicators (turns yellow as CO₂ is added).

Crystal violet is a triarylmethane dye. The dye is used as a histological stain and in Gram's method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and was formerly important as a topical antiseptic.

Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the amount of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colours in paints and inks.

Thymolphthalein is an acid-base (pH) indicator. Its transition range is at approximately pH 9.3-10.5. Below this pH, it is colorless; above this pH, it is blue. The molar extinction coefficient for the blue thymolphthalein dianion is 38000 M-1cm-1 at 595 nm.It can be used to make a disappearing ink

Victoria Blue BO, also known as C.I. Basic Blue 7 and C.I. 42595, is a chloride salt of a synthetic blue triarylmethane dye. Its chemical formula is C₃₃H₄₀N₃Cl. It has the appearance of a reddish blue powder. It is a photosensitizer.

Direct or substantive dyeing is normally carried out in a neutral or slightly alkaline dyebath, at or near boiling point, with the addition of either sodium chloride (NaCl) or sodium sulfate (Na₂SO₄). Direct dyes are used on cotton, paper, leather, wool, silk and nylon. They are also used as pH indicators and as biological stains.

Auramine O can be used to stain acid-fast bacteria (e.g. Mycobacterium), where it binds to the mycolic acid in its cell wall) in a way similar to Ziehl-Neelsen stain. It can also be used as a fluorescent version of Schiff reagent.

Coomassie Brilliant Blue is the name of two similar triphenylmethane dyes that were developed for use in the textile industry but are now commonly used for staining proteins in analytical biochemistry. Coomassie Brilliant Blue G-250 differs from Coomassie Brilliant Blue R-250 by the addition of two methyl groups.

Patent Blue V, also called Food Blue 5 or Sulphan Blue, is a dark bluish synthetic dye used as a food colouring. As a food additive, it has E number E131. It is a sodium or calcium salt of diethylammonium hydroxide inner salt. It has the appearance of a violet powder.

Reactive dyes utilize a chromophore attached to a substituent that is capable of directly reacting with the fibre substrate. The covalent bonds that attach reactive dye to natural fibres make them among the most permanent of dyes.  Reactive dyes are by far the best choice for dyeing cotton and other cellulose fibres at home or in the art studio.