Glycerin

Glycerin - Uses, Side Effects and Properties

Glycerol or more commonly called glycerin is, in simple terms, organic alcohol which is a mixture of sugar and alcohol and is fully miscible in water. Due to its properties, glycerin is used in a way or the other in nearly every industry. It is a simple polyol compound with three hydroxyl group (-OH) attached.





K. W. Scheele, the Swedish chemist, accidentally discovered glycerin in the late 1700s. One day he was heating a mixture of olive oil and litharge (lead monoxide) and in the course of the experiment, the glycerol was manufactured. Alcohol has been described by him as the "sweet principle of fat." Scheele later discovered that other metals and glycerides produce the same chemical reaction which yields glycerine and soap by a method called saponification, and, in 1783, he published a description of his method of preparation in the lab of Sweden. Scheele's technique was implemented to commercially manufacture glycerol for a few years.

In this chapter, we will extensively discuss its formation, physical and chemical properties along with the uses.

FORMATION:


  • 1. From Natural Sources

  • Glycerol is usually obtained from plant and animal sources where it is found in the form of in triglycerides, esters of glycerol with long-chain carboxylic acids. The reaction, saponification, or transesterification of these triglycerides produces glycerol as well as the fatty acid derivative:




    Triglycerides may be altered with hydroxide to present alcohol and fatty metal salt or soap.

  • 2. From Artificial Sources

  • Glycerol may be created by varied routes from propene. The epichlorohydrin method involves the chlorination of propylene to present allyl chloride, which is oxidized with hypochlorite to produce dichlorohydrins that in turn reacts with a strong base to give epichlorohydrin. This epichlorohydrin is then hydrolyzed to produce glycerol. Chlorine-free processes from propene are about the synthesis of an alcohol from acrolein and propene compound.




  • PHYSICAL PROPERTIES


    Physically, glycerol may be a soluble, clear, nearly colorless, odorless, viscous, hygroscopic liquid with a high boiling point. The boiling purpose of pure alcohol at gas pressure (760 mm) is 290 degrees C.

    Glycerol is of lower pressure than would be expected from its mass, due to the molecular association characteristic of alcohols. Many of the necessary uses of glycerol are mostly due to their relative in-volatility. Consequently, there are a variety of determinations of its pressure and its partial pressure in glycerine solutions. The pressure of 100% alcohol is below 0.001 (mm. Hg.) at room temperature, and below 0.2 mm. at 100" C.

    Hygroscopicity: Anhydrous alcohol contains a terribly high affinity for water, a property chargeable for its uses as a desiccant for gases. One of the important features is the capacity to absorb moisture and retaining it for long. It is the idea for its use as a substance, and conjointly for its use as an acquisition agent wherever each the alcohol itself and also the water it holds act as plasticizers.

    Temperature: The freezing point is most precisely at 18.17O degree Celsius. Glycerol is seldom seen in its crystallized state, because of its tendency to supercool, and the pronounced effect of small amounts of water in it.

    Thermal Conductivity: The thermal conduction of alcohol solutions will increase as their water content will increase. It conjointly will increase with rising temperature, the speed of modification being linear. 

    Viscosity: When glycerol is supercooled, its viscosity will gradually increase, and then a more rapid change from viscous liquid to a rigid glassy state occurs at a temperature range of -70 to -1 degree Celsius. When within the vitreous state, its physical constants lie nearer those of crystalline glycerol than liquid glycerol.

    IMPLEMENTATION OF CHEMICAL PROPERTIES


  • 1. Food and Beverages Industry

  •  In foods and beverages, glycerine mostly acts as a solvent, sweetener, and preservative. It serves the purpose of the solvent for flavors and food colors in case of soft drinks and confections and as a softening agent in food items like candy, cakes, and casings for meats and cheese. Glycerine is additionally employed in dry pet foods to assist retain wet and enhance taste property. Another important, but indirect, use of glycerine in food processing is represented by monoglycerides, the glycerol esters of fatty acids, which are emulsifiers and stabilizers for many products. Edible monoglycerides can be used to retain moisture balance in a product and allow richer formulations with an extended shelf life. It is even added to margarine to increase plasticity thus helping in the dispersion of fat. Monoglycerides have also found their uses in salad dressings, frozen desserts, candy, and food coatings.



  • 2. Drug:

  • Glycerine has found its vivid use in the drugs and pharmaceutical industries. It functions as a solvent, moistener, humectant, and bodying agent in tinctures, elixirs, ointments, and capsules for medicinal use. These are plasticized with glycerine. Other uses consist of ear infection remedies, suppositories, cough remedies, anesthetics, lozenges, gargles, and vehicles for antibiotics and antiseptics. Medically, alcohol is an emollient and demulcent in preparations used on the skin and used as a diffusion drug to manage cerebral swelling, scale back funiculus pressure.

  • 3. Urethane Polymers

  • In this application, glycerine serves as the fundamental building block in polyethers for urethane foams. The versatile foams ensuing from the processes utilizing glycerol have superior properties with regard to resilience. Glycerine-based polyethers have conjointly found some application in rigid foams and significantly, in urethane coatings.





    4. Nitration


    The nitration of alcohol resulting in the formation of nitroglycerin is perhaps the foremost well-known application. Dynamite, as it is manufactured today, is a mixture based on an explosive compound, usually nitroglycerine, mixed with an absorbent, usually diatomaceous earth, in a proportion of about 3:l nitroglycerine to the absorbent. It is additionally used as a vessel agent, functioning as a vasodilative in coronary spasm and as an antianginal agent. It has conjointly been used therapeutically for canine bronchial asthma.




    5. Metabolism in Human
    Glycerol could be a precursor for the synthesis of triacylglycerols and of phospholipids within the liver and fat. When the body uses to hold on fat as a supply of energy, alcohol and fatty acids are made free into the blood. Circulating glycerol does not glycate proteins as do glucose or fructose, and does not lead to the formation of advanced glycation end products (AGEs). In some organisms, the alcohol part will enter the metabolic process pathway directly and, thus, provide energy for cellular metabolism (or, potentially, be converted to glucose through gluconeogenesis).

    OTHER USES

    1.
    Paper and Printing


    Glycerine is employed within the manufacturing of papers as a plasticizer/humectant and stuff. In addition to the softening property retaining moisture, it conjointly reduces shrinkage. It is likewise helpful with alternative ingredients in specialty treatments like grease-proofing. Since many papers are used as food wrappers or in sanitary products, glycerine's essential nontoxicity, freedom from odor, and stability meet other important quality requirements. Glycerine conjointly finds in-depth use in ink manufacture, particularly the synthetic resin resins that area unit a very important constituent of the many printing inks.

    2. Cosmetics and Toiletries


    Glycerine is widely used in cosmetics and other toiletry applications, being virtually nontoxic, non-irritating, and odorless. It functions as an emollient. Glycerine could be a major ingredient for manufacturing toothpaste. Thus it prevents drying out and hardening within the tube and round the cap threads or at the gap of the dispenser. Other uses are in the manufacturing of skin creams and lotions, shaving preparations, deodorants, and makeup. Glycerol esters of fatty acids, a very important category of glycerol derivatives, are utilized as emulsifiers in creams and lotions and as replacements for waxes in lipstick, in mascara, and in other non-greasy emulsions

    3. Textiles


    Glycerine could be a textile acquisition agent used wide in lubricating, sizing, and softening yarn and fabric. Its effectiveness in these and similar applications is due to its consistency and hygroscopicity. Glycerine is additionally accustomed lubricate for several styles of fibers used in spinning, twist setting, knitting. and weaving operations.

    4. Tobacco


    A glycerol content of nearly 3 percent keeps tobacco wet and soft so that breaking and crumbling throughout the process can be prevented and freshness in prepacked cigarettes and alternative tobacco product can be ensured. Sheet-formed cigar tobacco is plasticized with glycerine. It also adds flavor to chewing and pipe tobaccos. Niacetin (glycerol triacetate) acts as a plasticizer for cellulose acetate in the manufacture of cigarette filter-tips.

    5. Electrical and Electronics


    Glycerine is widely used for the manufacture of electrolytes for electrolytic condensers utilized in radios. Electronic applications are mostly of a proprietary nature. Although one use during this field is related to the assembly of computers.
    There are many other applications for glycerine. These uses are small in volume and include such applications as photography, laboratory use, cell preservation, and gas drying among many others too numerous to list. Applications for a few glycerol derivatives have conjointly been mentioned. It is worth noting that they include ethers, esters, acetates, and alcohol substitution products. New uses, several proprietaries, for glycerol and its derivatives come back beneath constant development as technology progresses.