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an example of a weak acid in the human body that serves as an effective buffer

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From Wikipedia

Acid dye

An acid dye is a dye, in chemical regard a sodium (less often–ammonium) salt of a sulfonic, carboxylic or phenol organic acid. Acid dye is soluble in water and possesses affinity for amphoteric fibers while lacking direct dyes' affinity for cellulose fibers. When dyeing, ionic bonding with fiber cationic sites accounts for fixation of colored anions in the dyed material. Acids are added to dyeing baths to increase the number of protonated amino-groups in fibers.

Some acid dyes are used as food colorants.



In the laboratory, the home or art studio, the acid used in the dyebath is often vinegar (acetic acid) or citric acid. The uptake rate of the dye is controlled with the use of sodium chloride. In textiles, acid dyes are effective on protein fibers, i.e. animal hair fibers like wool, alpaca and mohair. They are also effective on silk. They are effective in dyeing the synthetic fibernylon but of minimal interest in dyeing any other synthetic fibers.


In staining for microscopic examination for diagnosis or research acid dyes are used to color basic tissue proteins in contrast to basic dyes, which are used to stain cell nuclei and some other acidic components of tissues.


Acid dyes are generally divided into three classes which depend on fastness requirements, level dyeing properties and economy. The classes overlap and generally depend on type of fiber to be colored and also the process used.

Acid dyes are thought to fix to fibers by hydrogen bonding, Van der Waals forces and ionic bonding. They are normally sold as the Sodium salt therefore they are in solution anionic. Animal proteinfibers and syntheticNylon fibers contain many cationic sites therefore there is an attraction of anionic dye molecule to a cationic site on the fiber. The strength (fastness) of this bond is related to the desire/ chemistry of the dye to remain dissolved in water over fixation to the fiber.

History of acid dye


The chemistry of acid dyes is quite complex. Dyes are normally very large aromatic molecules consisting of many linked rings. Acid dyes usually have a sulfo or carboxy group on the molecule making them soluble in water. Water is the medium in which dyeing takes place. Most acid dyes are related in basic structure to the following:

Anthraquinone type:

Many acid dyes are synthesised from chemical intermediates which form anthraquinone-like structures as their final state. Many blue dyes have this structure as their basic shape. The structure predominates in the levelling class of acid dye.

Azo dyes:

The structure of azo dyes is based on azobenzene, Ph-N=N-Ph (see right showing cis/ trans isomers) Although Azo dyes are a separate class of dyestuff mainly used in the dyeing of cotton (cellulose) fibers, many acid dyes have a similar structure, and most are red in color.

Triphenylmethane related:

Acid dyes having structures related to triphenylmethane predominate in the milling class of dye. There are many yellow and green dyes commercially applied to fibers that are related to triphenylmethane.

Classes of acid dyes

Equalising/levelling acid dyes: Highest level dyeing properties. Quite combinable in trichromatic shades. Relatively small molecule therefore high migration before fixation. Low wet fastness therefore normally not suited for apparel fabric.

Milling acid dyes: Medium to high wet fastness. Some milling dyes have poor light fastness in pale shades. Generally not combinable. Used as self shades only.

Metal complex acid dyes: More recent chemistry combined transition metals with dye precursors to produce metal complex acid dyes with the highest light fastness and wet fastness. These dyes are also very economical. They produce, however, duller shades.

Health and safety

Any dyes including acid dyes have the ability to induce senstisation in humans due to their complex molecular structure and the way in which they are metabolised in the body. This is extremely rare nowadays as we have a much greater understanding through experience and knowledge of dyestuffs themselves. Some acid dyes are used to colour food. We wear fabrics every day exposing our skin to dyes.

The greatest risk of disease or injury due to dyes is by ingestion or exposure to dye dust. These scenarios are normally confined to textile workers. Whereby the dye itself is normally non toxic, the molecules are metabolised (usually in the liver) where they may be broken back down to the original intermediates used in manufacture. Thus many intermediate chemicals used in dye manufacture have been identified as toxic and their use restricted. There is a growing trend among governments to ban the importation of dyes synthesised from restricted intermediates. For example: the dye CI Acid red 128 is banned in Europe as it was found to metabolise in the body back to ortho-toluidine, one of its chemical intermediates. Many intermediates used in dye manufacture such as o-toluidine, benzidine etc. were found to be carcinogenic. All the major chemical companies have now ceased to market these dyes. Some, however, are still produced but they are found to be totally safe when on the fiber in its final state. The use of these dyes is declining rapidly as cheap and safer alternatives are now easily available.

The incident concerning the dye Sudan 1 is an example of a suspected toxic dye finding its way into the food chain. Such incidents are extremely rare.

From Encyclopedia

Amino Acids

Amino acids are organic compounds made of carbon, hydrogen, oxygen, nitrogen, and (in some cases) sulfur bonded in characteristic formations. Strings of amino acids make up proteins, of which there are countless varieties. Of the 20 amino acids required for manufacturing the proteins the human body needs, the body itself produces only 12, meaning that we have to meet our requirements for the other eight through nutrition. This is just one example of the importance of amino acids in the functioning of life. Another cautionary illustration of amino acids' power is the gamut of diseases (most notably, sickle cell anemia) that impair or claim the lives of those whose amino acids are out of sequence or malfunctioning. Once used in dating objects from the distant past, amino acids have existed on Earth for at least three billion years—long before the appearance of the first true organisms. Amino acids are organic compounds, meaning that they contain carbon and hydrogen bonded to each other. In addition to those two elements, they include nitrogen, oxygen, and, in a few cases, sulfur. The basic structure of an amino-acid molecule consists of a carbon atom bonded to an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a fourth group that differs from one amino acid to another and often is referred to as the-R group or the side chain. The-R group, which can vary widely, is responsible for the differences in chemical properties. This explanation sounds a bit technical and requires a background in chemistry that is beyond the scope of this essay, but let us simplify it somewhat. Imagine that the amino-acid molecule is like the face of a compass, with a carbon atom at the center. Raying out from the center, in the four directions of the compass, are lines representing chemical bonds to other atoms or groups of atoms. These directions are based on models that typically are used to represent amino-acid molecules, though north, south, east, and west, as used in the following illustration, are simply terms to make the molecule easier to visualize. To the south of the carbon atom (C) is a hydrogen atom (H), which, like all the other atoms or groups, is joined to the carbon center by a chemical bond. To the north of the carbon center is what is known as an amino group (-NH2). The hyphen at the beginning indicates that such a group does not usually stand alone but normally is attached to some other atom or group. To the east is a carboxyl group, represented as-COOH. In the amino group, two hydrogen atoms are bonded to each other and then to nitrogen, whereas the carboxyl group has two separate oxygen atoms strung between a carbon atom and a hydrogen atom. Hence, they are not represented as O2. Finally, off to the west is the R -group, which can vary widely. It is as though the other portions of the amino acid together formed a standard suffix in the English language, such as -tion. To the front of that suffix can be attached all sorts of terms drawn from root words, such as educate or satisfy or revolt —hence, education, satisfaction, and revolution. The variation in the terms attached to the front end is extremely broad, yet the tail end, -tion, is a single formation. Likewise the carbon, hydrogen, amino group, and carboxyl group in an amino acid are more or less constant. The name amino acid, in fact, comes from the amino group and the acid group, which are the most chemically reactive parts of the molecule. Each of the common amino acids has, in addition to its chemical name, a more familiar name and a three-letter abbreviation that frequently is used to identify it. In the present context, we are not concerned with these abbreviations. Amino-acid molecules, which contain an amino group and a carboxyl group, do not behave like typical molecules. Instead of melting at temperatures hotter than 392°F (200°C), they simply decompose. They are quite soluble, or capable of being dissolved, in water but are insoluble in nonpolar solvents (oil-and all oil-based products), such as benzene or ether. All of the amino acids in the human body, except glycine, are either right-hand or left-hand versions of the same molecule, meaning that in some amino acids the positions of the carboxyl group and the R -group are switched. Interestingly, nearly all of the amino acids occurring in nature are the left-hand versions of the molecules, or the L-forms. (There-fore, the model we have described is actually the left-hand model, though the distinctions between "right" and "left"—which involve the direction in which light is polarized—are too complex to discuss here.) Right-hand versions (D-forms) are not found in the proteins of higher organisms, but they are present in some lower forms of life, such as in the cell walls of bacteria. They also are found in some antibiotics, among them, streptomycin, actinomycin, bacitracin, and tetracycline. These antibiotics, several of which are well known to the public at large, can kill bacterial cells by interfering with the formation of proteins necessary for maintaining life and for reproducing. A chemical reaction that is characteristic of amino acids involves the formation of a bond, called a peptide linkage, between the carboxyl group of one amino acid and the amino group of a second amino acid. Very long chains of amino acids can bond together in this way to form proteins, which are the basic building blocks of all living things. The specific properties of each kind of protein are largely dependent on the kind and sequence of the amino acids in it. Other aspects of the chemical behavior of protein molecules are due to interactions between the amino and the carboxyl groups or between the various R -groups along the long chains of amino acids in the molecule. Amino acids function as monomers, or individual units, that join together to form large, chainlike molecules called polymers, which may contain as few as two or as many as 3,000 amino-acid units. Groups of only two amino acids are called dipeptides, whereas three amino acids bonded together are called tripeptides. If there are more than 10 in a chain, they are termed polypeptides, and if there are 50 or more, these are known as proteins. All the millions of different proteins in living things are formed by the bonding of only 20 amino acids to make up long polymer chains. Like the 26 letters of the alphabet that join together to form different words, depending on which letters are used and in which sequence, the 20 amino acids can join together in different combinations and series to form proteins. But whereas words usually have only about 10 or fewer letters, proteins typically are made from as few as 50 to as many as 3,000 amino acids. Because each amino acid can be used many times along the chain and because there are no restrictions on the length of the chain, the number of possible combinations for the formation of proteins is truly enormous. There are about two quadrillion different proteins that can exist if each of the 20 amino acids present in humans is used only once. Just as not all sequences of letters make sense, however, not all sequences of amino acids produce functioning proteins. Some other sequences can function and yet cause undesirable effects, as we shall see. DNA (deoxyribonucleic acid), a molecule in all cells that contains genetic codes for inheritance, creates encoded instructions for the synthesis of amino acids. In 1986, American medical scientist Thaddeus R. Dryja (1940-) used amino-acid sequences to identify and isolate the gene for a type of cancer known as retinoblastoma, a fact that illustrates the importance of amino acids in the body. Amino acids are also present in hormones, chemicals that are essential to life. Among these hormones is insulin, which regulates sugar levels in the blood and without which a person would die. Another is adrenaline, which controls blood pressure and gives animals a sudden jolt of energy needed in a high-stress situation—running from a predator in the grasslands or (to a use a human example) facing a mugger in an alley or a bully on a playground. Biochemical studies of amino-acid sequence

From Yahoo Answers

Question:How are acids and bases used in our body to control the PH of our blood, digest food, and construct macromolecules? Websites and other information links please too. Thanks guys :D Thanks down there! Do you have any recourses? Websites or anything. Definitely helped.

Answers:The control of pH in the body is performed by buffers. A buffer is a solution of a weak acid and its conjugate base that can absorb H+ and OH- with little change in pH. This is what keeps the pH of our blood, for instance, at a relatively constant 7.4. Should blood become more or less acidic than that and we would suffer from conditions known as alkalosis and acidosis, both of which, if not corrected, can result in death. In our blood, the buffer system consists of dissolved CO2 and bicarbonate ion (HCO3-). (Despite what you might see in some textbooks, there is no H2CO3 in blood. H2CO3 as a molecule cannot exist in an aqueous solution, including blood. Carbonic acid actually consists of this equilibrium: CO2(aq) + H2O(l) <==> H+ + HCO3-. An important use for an acid is in the stomach. The liquid in the stomach is a mixture of a number of substances including H+ and Cl-, which of course, are found in hydrochloric acid. The "HCl" in the stomach is about 0.1M to 0.01M.

Question:How does the carbonic buffer system work? How would you use the Herdersen-Hasselbalch equation to determine the ratio and concentration of bicarbonate to carbonic acid to prove if it is a good enough buffer for the body? example numbers: pH=7.55 pK of HCO3 is 10.33 conc of HCO3 in blood is 21mM

Answers:The "carbonic acid" system: CO2(aq) + H2O <==> H+ + HCO3- -- Ka = 4.3 x 10^-7 You will notice the absence of H2CO3. That is because there is no H2CO3. As a molecule, It does not exist in aqueous solution. What we have called carbonic acid in the past is the equilibrium system of carbon dioxide, water, hydrogen (hydronium) ions and bicarbonate ions. Clearly, it is a good buffer system because evolution has selected it to maintain the pH of our blood. The Henderson-Hasselbalch equation is an equation which approximates the pH of a buffer system based on the concentrations of a weak acid and its conjugate base, and the assumption that concentration of the undissociated acid does not change. pH = pKa + log([base]/[acid])


Answers:I presume you're asking in regard to the human body so I'll try to answer in that area. As some of the other answers have stated "acid" is hydrogen ions which are acidic and must be maintained within fairly strict limits. Normaly the total number of hydrogen ions in the body at any given time is high, because of this the ph system is used. The ph scale is inversely related to hydrogen concentration. Hydrogen down/ph up. Hydrogen up/ ph down. The ph scale is logarithmic with each number representing a value 10 times its neighboring number. For example a ph 6 has a hydrogen ion concentration 10 times greater than ph 7. The scale runs from 1 - 14. The ph of water is 7.0 which is neutral, the ph of the body is normally 7.35-7.45. Above that is called alkalosis, below acidosis. The body is constantly producing hydrogen ions through metabolism and to maintain the acid-base balance they must be constantly eliminated from the body. The fastest way is the buffer system or the bicarbonate buffer system. The 2 components are the bicarbonate ion and carbonic acid. Carbonic acid is a weak acid that is tolerated than the hydrogen ion. There are a couple forms of acidosis and alkalosis , respiratory and metabolic. This particular subject is one that gives paramedics fits while in school when they are first introduced to it so if you're having problems with it you're just normal. One day it will just become clear and you'll wonder what the problem was all along. I've taught this subject on occasion and am quite accustomed to the glazed eyes sorta like the deer in the headlight syndrome when first introduced to it. Best of luck with your class.

Question:Here is the list of substances we are using: 5 mL 0.10 M HC2H3O2 + 5 mL H2O 50 mL 0.10 NH3 + 50 mL 0.10 M NH4NO3 10 mL 0.10 M NH4NO3 + 5 mL 0.10 M NaOH So, those are 3 examples of a list of 12 I have. The things I need to determine are: Which substances are strong acids and strong bases? Which substances are weak acids and weak bases? Which solutions should exhibit common ion effects? Which solutions are buffers? If you could help me out with common guidelines for determining those things, it would really help me. I am also wondering what parts of those solutions are relevant to the questions.. how much does it matter the amount in mL there is? How does it effect the concentration.. is it diluting the substance then? Thank you!

Answers:You have to memorize (or look up) the strong/weak acids/bases. The strong acids are: HClO4, HI, HBr, HCl, H2SO4, HNO3 The strong bases are: KOH, Ba(OH)2, NaOH, Sr(OH)2, Ca(OH)2, LiOH, Sr(OH)2, RbOH Hope this helps!