Daily we come across numerous amalgams which chemists categorize as acids or tart. There are several kinds of acids, including citric acid contained in orange and grape juices. Orange, grape and other fruit saps also have ascorbic acid, which is better known as vitamin C. Again, vinegar is another acid - acetic acid - that is added to green salads for taste. Boric acid is another tart that is used to cleanse the eyes.

Again, all chemistry laboratories possess different types of acids like nitric, hydrochloric, and sulfuric acid. These tarts are different from the acids used in the households and are derived from amalgams known as minerals. These are stronger acids and unless handled and used carefully, they may lead to serious physical damages like smoldering skins or burn up the clothing.

All acids are sour in flavor. For instance, citric acid present in lemons, limes, grapes and oranges is responsible for the tart flavor of these fruits. Similarly, vinegar is sour because of the presence of acetic acid.

How do we test acids or know whether a substance is acidic or not? As most are aware, acids are tested by indicator papers known as litmus paper. Litmus is a colorant that is derived from dying chemicals from vegetables and they come in two colors - red and blue based on the tartness of the substance. While red litmus is processed by acids and hence do not change color when any acid is poured on it, blue litmus is derived from alkaline substances and hence when acid is dropped on it, the paper changes color and turns red.

Talking about the formation of acids, these tarts comprise merged hydrogen. For example when a highly rash metal like zinc is dropped in a test tube containing acid like hydrochloric acid an effect takes place. The fizz inside the tube signifies that a gaseous substance has been let loose. And if you want to test the gas formed from the reaction between zinc and hydrochloric acid, just put in a burning splint inside the test tube and you will be surprised to notice the gas rupture into a blaze producing a pop noise. This proves that the reaction between zinc and hydrochloric acid had produced hydrogen gas, as this gas burns with a popping sound in the presence of oxygen. And the second thing to remember is that when specific acids counter metals, the reaction produces hydrogen gas.

It is also essential to keep in mind that acids produce hydrogen in water solutions and that acids always dissolve in water to generate acid ionizes. On the face of it, when acids react with water, they are generally diluted, but a closer look into the matter reveals that the reaction produces hydrogen ions and also ions of a non-metal or non-metallic polyatomic ion. Therefore, following this rule, when you liquefy hydrochloric acid in water, the acid ionizes, producing hydrogen and chloride ions.

Feeble acids comprise a major part of all plant substances, but comparatively very little of it exist in free form and hence most of the plants don't taste sour or bitter. On the contrary, usually the acids present in the plants are basically found in the mode of their salts, esters or amides, and even in fat or lipid form that are actively soluble. Although, most chemists who are more concerned to extract powerful chemicals from the plants still continue to ignore the acid forms present in the plants like many other types of plant constituents, their action is often substantial in the background of a total herbal prescription, and is a significant aspect in the property of fruit and vegetable consumptions.

The acids that are derived from the plants are usually carboxylic acids that have a common formula RCOOH. There are four main categories of acids that are extracted from plants and they are as following:

  • Aromatic acids: going by their name, aromatic acids are cyclic acids generally based on cinnamic and benzoic acids and provide some kind of aroma. These tarts and their by-products are scattered in nature, especially in resins and balsams. By-products or off-shoots of benzoic acid comprise the phenols and salicylic acid, and the tannins. Again, one by-product or derivative of cinnamic acid is umbelliferone belonging to the parsley relatives.
  • Polybasic acids: as the name poly suggests these acids comprise more than one carboxyl group and are commonly found in plant substances and include fumaric, oxalic, and succinic acids. Polybasic acids usually possess a slightly laxative consequence along with their own specific effects.
  • Monobasic (monocarboxylic) acids: these straight-chain acids comprise up to twenty-six carbons for each molecule. These tarts consist of formic as well as acetic acids, along with the saturated and unsaturated fatty acids, and valeric acid which is derived from popular herbs like hops (Humulus lupulus) and valerian (Valeriana officinalis).
  • Hydroxy acids: the name of these acids makes it clear that they comprise both a pair of carboxyl groups and one hydroxyl group, imparting them the features of acids and alcohols. Hence these acids can produce polyesters. However, the most important pharmacological property of hydroxyl acids is their capacity to impound and efficiently counteract cations, like the ions of copper, calcium, iron and manganese. Hydroxy acids comprise following acids: citric, malic and tartaric.

Uses of acids

Amongst the rest of chemical substances, sulfuric acid is a compound that is used most commonly for industrial purpose. The acid is not only used in isolation, but also exploited to prepare other tarts like hydrochloric and nitric acid simply owing to its comparatively higher boiling point. Other acids boil at much lower temperatures and so it permits the sulfuric acid to be produced for distillation and collection individually from the initial material.

Sulfuric acid is also a very effective anti-rust material and is applied on the surface of metals to eradicate oxide layers through a process called pickling before the metals are layered with substances that prevent them from rusting. The chromium coating of iron is an ideal example of this phenomenon. The process for chromium plating is simple too. Prior to coating iron with chromium, it is dipped in diluted sulfuric acid to remove the oxide lawyer present on its surface. Sulfuric acids also play a vital role in storage cells. Diluted sulfuric acid acts as an electrolyte in a lead storage cells and enables the movement of ions between the lead plates, that perform the task of cathodes, while the spongy lead dioxide act as anodes. In fact, if you have a closer look at the automobile batteries, you will find that many such lead storage cells are connected together make up this type of storage battery.

Among other acids that have immense value in industrial use is nitric acid, which is profusely used to manufacture fertilizers, plastics, photographic film, and even dyes. In addition to these industrial uses, nitric acid is also utilized in preparing explosives like dynamite (TNT).

Like sulfuric acids, hydrochloric acids also are useful while cleaning metals. Apart from cleaning metals, hydrochloric acid is also used to make bricks and tiles dirt-free and surprisingly, also in the manufacturing of sugar and glue. And although it may appear to be incredible to many, hydrochloric acid is generated in small quantities in our stomachs to help digest the food stuff that we consume.

Fatty acids are another chemicals that are found in unsaturated conditions in plants and even in animal tissues. Contrary to the common belief, fatty acids are found more commonly in plants rather than in animal tissues. Many may dismiss fatty acids as reasons for obesity, but this particular acid is essential to build and repair the cell structures like the cell wall, and important tissues in the central nervous system. At the same time, fatty acids are needed to generate the raw material for manufacturing prostaglandin. It may be noted here that when there is a deficit of PUFAs (polyunsaturated fatty acids) in the bloodstream, it leads to inciting and chronic diseases.

Unlike most other acids, fatty acids occur in about forty different types in nature. However, fatty acids can be classified under two broad categories - saturated and unsaturated. When fatty acids are without carbon-carbon double bonds they are known as saturated, while fatty acids enclosing carbon-carbon double bonds are said to be unsaturated. Among the saturated fatty acids, palmitic and stearic acids are the most widespread, while oleic and linoleic acids are the most common unsaturated fatty acids. Oleic acid is also known as mono-unsaturated since it has only one carbon-carbon double bond. On the other hand, linoleic, linolenic, and arachidonic acids are said to be poly-unsaturated as they comprise two, three, and four carbon-carbon double bonds, correspondingly.

Well, now how do you measure the comparative degree of unsaturation of fat or oil? It may be noted here that the simplest way to calculate this is to ascertain the fat or oil's iodine number. And what is this iodine number? Simply speaking, the iodine number is the weight or mass of iodine in grams that is burnt up by or reacts with 100 grams of a fat or oil. In fact, iodine enters into a chemical reaction with the carbon-carbon double bonds and hence, more the number of double bonds, the higher the iodine number in the fat or oil. Generally, fats have lower iodine numbers compared to oils that possess greater percentages of carbon-carbon bonds and these are double bonds.

Of late, PUFA, usually created by the body from arachidonic acid, di-homo-y-linolenic acid (GLA), a major constituent of the oil of the evening primrose (Oenothera biennis spp.), which is used in the healing of a range of rabble-rousing disorders. Even inflammatory diseases like rheumatoid and eczema conditions as well as premenstrual syndrome and all such conditions would most probably be based on a shortage of innate production of GLA by the person involved have been treated by application of PUFA.

Formic acid

Having the lowest molecular weight and being one of the most simple of carboxylic acids, formic acid is a pale, acerbic liquid that has a sharp smell. It boils at 100.7°C, a temperature higher than the boiling point of water, and solidifies at 8.4°C. Formic acid has an interesting feature and it acts both as an acid as well as an aldehyde and has qualities of both. Hence, functioning as an acid, formic acid enters into chemical reactions with most alcohols to produce esters and crumbles or decomposes when it is heated. Again, showing features of an aldehyde, formic acid oxidizes effortlessly.

In nature, formic acid can be found in the bodies of red ants and in the bees' stingers. Normally, it is possible to produce formic acid in small quantities by oxidizing formaldehyde, while commercial or industrial production of formic acid is done by heating carbon monoxide and sodium hydroxide to form sodium formate. The sodium formate is then cautiously reacted with sulfuric acid and the resultant is formic acid. Among the most common industrial uses of formic acid are textile dyeing, coagulating latex rubber and in leather tanning.

Formic acid is also mentioned in medical history. In the ancient days some people used the chemical to treat chronic joint inflammations by causing local irritants. The corrosive feature of the substance causes an inflammatory reaction when applied on skin and earlier formic acid was used as one of various treatments for counter-irritants and blistering agents or vesicants. It used to be applied in a less injurious way to avoid damaging congested joint. In fact, formic acid forms an important module in the sting of the European stinging nettle (Urtica spp.). Exposure to formic acid has conventionally been linked with a lower frequency of arthritic disorder. Incidentally, the Romans generally recommended thrashing with bunches of nettles over affected joints. Though, formic acid does not endure cooking or other preparations, as it quickly oxidizes to carbon dioxide and water. Formic acid, however, plays no role in the holistic medicine.

Acetic acid

Acetic acid, the main element of vinegar, is a dull and water soluble liquid with a pungent smell. There are numerous processes through which the tart can be produced. Among the many methods one is by oxidizing acetaldehyde, while another is by reacting ethyl alcohol with bacteria. It can also be derived from a chemical reaction between methyl alcohol and carbon monoxide. Unlike many other substances, acetic acid is seldom found in living plants. Among its uses are manufacture of acetate fibers and preparation of a number of solvent and food flavoring esters. Acetic acid imparts a special characteristic to substances prepared with it. Like vinegar which is used as a preservative, in traditional medicine acetic acid was used to conserve liquid medicines made from herbs. As a consequence, these medicines could be stored effectively for very long periods. The Chinese added acetic acid in liquid herbal medicines to impart special qualities to them and obtain different form of remedies from them. In modern times, many propound the theory that vinegar can be used to treat various toxic states, but this practice is yet to gain popularity or be accepted by the masses.

Oxalic acid

First discovered in the sap of the wood sorrel type of oxalis, oxalic acid is a colorless, crystalline, water-soluble, poisonous acid that is primarily used as a laboratory reagent, cleanser or for bleaching purposes. Oxalic acid can be acquired in many ways. One way to obtain oxalic acid is to chemically reacting carbon monoxide with sodium hydroxide, while it can also be derived by reacting specific carbohydrates with acids or alkalis. These reactions lead to the formation of insoluble salts along with substances like calcium. While oxalic acid in this form is especially found in the dock and rhubarb families like Rumex and Rheum spp. Interestingly, though poisonous in nature, oxalic acid is also found in many common foods like tea, spinach, beet and parsley and in many plants in small quantities. At times, oxalic acids also pose a health hazard and this is when precipitation of excessive oxalates in acid urine leads to urinary stones. Thus, in order to avoid urinary or kidney stones it is necessary to determine the problems faced by people and avoid food stuff with high levels of oxalate.

Succinic acid

Generally found in amber, lignite as well as many plants and also produced artificially during alcoholic fermentation. Succinic acid is a dull and crystalline dibasic acid. In all plant materials, succinic acid is an inconsistent ingredient. Succinic acid is useful in medicine preparations as well as in organic synthesis. Succinic acid also acts as an agent in the metabolism method in the human body by kindling tissue oxidation. Succinic acid is often used with salicylates by allopath physicians to treat arthritis and also as a medication for barbiturate poisoning. As mentioned earlier, succinic acid helps in tissue oxidation resulting to augmented blood gush and this is often desirable, especially in degenerative environments.

Tartaric acid

Tartaric acid is a colorless crystalline dicarboxylic tart that is present in many plants and fruits. Tartaric acid ensues as three separate isomers, namely the dextro-, levo-, and meso- forms and is widely found in fruits like grapes and tamarinds. While the dextro- and levo- forms of tartaric acid are optically functional, the meso- form is optically dormant like racemic acid, which is a mixture of equal parts of the dextro- and levo- forms. Unlike oxalic acid, tartaric acid cannot be disintegrated through digestion or metabolism of the body and hence it is emitted completely through the urine. Therefore, while most fruit acids get into the system and are beneficial to the body in one way or the either, tartaric acid augments acid intensity in the body. Then again, tartaric acid can not be naturally sucked up by the body and hence it suitably acts as a mild osmotic or water-attracting sap. Widely found in nature, tartaric acid is predominantly the dextrorotatory d-tartaric acid and is also known as d-2, 3-dihydroxysuccinic acid or 1-2,3-dihydroxybutanedioic acid. Interestingly, this variety of tartaric acid can be somewhat changed to the others forms by warming it up with a liquid alkali like potassium hydroxide. Tartaric acids can be obtained artificially by chemically treating maleic acids or fumaric acids with liquid potassium permanganate. The diverse isomeric varieties of tartaric acid can have different physical properties like their boiling points. The main use of tartaric acid is in the different varieties of its salts like Rochelle salt and cream of tartar.

Citric acid

Citric acid is a natural acid that is found in most sour fruits, including grapefruit, oranges, lemons, limes, gooseberries, peaches, plums and  pineapples. However, citric acid cannot be mistaken to be vitamin C, which is ascorbic acid. Most people mix these two up ignorantly or unwittingly. Interestingly, when any substance containing citric acid is consumed, it degenerates into bicarbonates. This reaction ironically is like an alkaline food stuff that results to arthritis and other relapsing diseases, which are caused by some fruit acids. Another irony of consuming food stuff consisting citric acid is that it lowers the propensity of tooth decay. The primary properties of citric acid is that it is able to curb the spread of bacteria in the mouth directly by invigorating salivary secretions that guarantees the beneficial alkaline and bacteria - prevent saliva blushes the mouth free of food material.

What is apparent is that along with other acerbic-flavoring substances, citric acid also leads to an enhanced secretion of bile from the liver. This is primarily owing to an outcome arbitrated by the motivation of the acerbic receptors in the oral cavity and this perhaps clarifies why people conventionally use huge amount of lemon juice with olive oil to wash out bile stones. Similar to tartaric acid, citric acid also has properties of being a mild osmotic sap and diuretic. Thus, when one takes into consideration the influences of vitamin C and the bioflavonoids they only emphasize on the fact that fruits are great food stuff as far as cleansing or detoxification of the body is concerned.

Benzoic acid

Benzoic acid is one of the simplest aromatic carboxylic acids that are found as a crystalline solid in nature, having a melting point at 122°C and boiling at 249°C. While benzoic acid like gum benzoin can be found in nature from resins, the tart can also be obtained artificially by amalgamating various organic combinations like benzyl alcohol, benzaldehyde, phthalic acid and toluene.

As mentioned earlier, benzoic acid is the most important ingredient of gum benzoin and can generally be located in high levels in Peru and Tolu balsams as well as in cranberries. When applied in lesser strengths or in a diluted state, benzoic acid is an effective local antiseptic, but a more concentrated version of the acid acts as a local aggravation. When used internally, benzoic acid has similar effects. It acts as an intestinal sterilizer and a latent irritant inside the body. When benzoic acid is taken in, it functions as a strong antipyretic that can be compared to or even exceed the outcome of salicylic acid. Among its medicinal uses, benzoic acid enhances the rate of metabolism and the use of protein by the body.

Locally, benzoic acid and the benzoates are usually made use of as inhalants and throat medication. Preparations from benzoic acid like Friar's Balsam are useful for clearing upper respiratory catarrh and have sterilizing, calming and caustic features. Basically, benzoic acid is mostly utilized to prepare its salts and esters like sodium benzoate. It may be noted here that sodium benzoate is commonly used as additives in food stuff and drinks and also as moderate sterilizers in all mouthwashes and toothpastes.


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