What is Glycerin?
- 1 What Is Glycerin
- 1.1 Name significance and alternative names
- 1.2 History
- 1.3 Chemical information
- 1.4 Sources of glycerin
- 1.5 Common uses of glycerin
- 1.6 Side effects of glycerin
- 1.7 Glycerin and the environment
What Is Glycerin
Glycerin is a liquid, alcohol-based substance derived from animal or vegetal fats. The pure glycerin is colorless, odorless, has a sweet taste and it is hygroscopic (it attracts water). Boosting a great variety of uses (over 1500 end uses); this substance is highly popular in cosmetic industry and food production industry. Pharmaceutical industry also relies heavily on glycerin, both as an active substance and as an excipient. It is estimated that 1.1 – 1.2 billion pounds of glycerin are consumed each year worldwide to produce a wide array of products, varying from skin creams to urethane foams. And the quantity is in full growth as the less developed countries adopt the substance for local industry usage.
Because of its extensive use, many people get in contact with glycerin, so it is imperative to have some basic information about the substance in order to best understand how it affects you when ingested, applied on skin and hair or used in any other way.
Name significance and alternative names
The word “glycerin” is derived from ‘glykeros’, a Greek word which means “sweet. The term was coined by Michael-Eugene Chevreul, a French chemist, in 1838.
Glycerin is also known under the name of glycerol (the more formal designation), glicerine (commonly used in British English), glyceritol, gycyl alcohol and osmoglyn. Less known names are propanetirol, propane -1, 2, 3-triol and 1, 2, 3 –trihydroxypropane, all derived from its chemical formula.
Glycerin, as known today, was discovered two centuries ago. However, its existence numbers more than four millennium. To be more exact, since around 2800 BC when the first soaps were made in ancient Babylon. The mixture of ashes, sesame oils, cypress oils and perfumed oils resulted in glycerin soaps, perfect to wash out dirt and leave the skin moisturized. The Egyptians started using soap around 1500 BC and their formula also contained a mix of oils and ashes which turned into nice smelling, moisturizing glycerin soaps.
In modern times, the chemical substance was discovered by K.W. Scheele by accident, during a chemical experiment which involved mixing olive oil with lead monoxide. He called this new substance the “sweet principle of fat. » The discovery was first documented in 1783, when he also detailed the method of obtaining glycerin in Transactions of the Royal Academy of Sweden. A French chemist, Pelouze, wrote the first chemical formula for glycerin (C3H803), while in 1883 the final formula used nowadays was presented by Berthelot and Lucea (C3H5(OH)3).
In the 17th century, glycerin was a by-product of candle making and had no specific use. Its extraction from soap was neither known, nor useful in any way. Its economic and industrial role debuted in 1866, when Alfred Nobel invented the dynamite, after a scientific work of over twenty years.
Chemical formula: C3H803. Glycerin has a molecular weight of 92.09 and a structural formula which highlights two primary hydroxyls and secondary ones.
- Melting point – 18.17 degrees Celsius
- Boiling point – 290 degrees Celsius
- Density – 1.261 g/cm3
- Viscosity – 1499 c.p. at 20 degrees Celsius (100% glycerol)
- Solubility – glycerin is soluble in water and alcohol and slightly soluble in ether, ethyl acetate and dioxane. It is not soluble in hydrocarbons.
- Solvent – glycerol is a good solvent for a multitude of substances, both organic and inorganic, which makes it suitable for pharmaceutical use. Its solvent properties are similar to water.
Glycerin is an alcohol and undergoes the same reactions of an alcohol. The reactive property is more present in the two primary hydroxyl groups than in the middle secondary group. The reactions with glycerin are best carried in neutral or alkaline environment, at temperatures under or equal to 180 degrees Celsius. Water is absorbed by glycerin, case in which the glycerin is more rapidly attacked by microorganisms.
Sources of glycerin
Originally present only in home-made soaps and as a by-product of candle-making, glycerin is now obtained through different chemical procedures. The traditional way, called saponification, is still preferred today as it offers pure glycerin which can be used in cosmetic and food industry. The chemical process, on the other hand, offers a higher quantity of substance, with a low quality, which can hardly be refined and re-used for human consumption. Let’s take a look at each one of these processes for a better understanding of the phenomenon.
Hydrolysis or Saponification
The process through which fats (vegetable or animal) are combined with lye in order to produce soaps is called saponification or hydrolysis. Through this process the fats and lye are transformed into glycerin soap. It is important to understand that all soap resulted after hydrolysis contains glycerin. However, due to its higher commercial value, glycerin is usually extracted from the soap and sold separately to different industries using it. A small quantity of glycerin is left in the soap bars. This means that most soap do not moisturize the skin, but rather dry it out because of their aggressive composition.
The glycerin extracted after the hydrolysis process is pure and can be used in food industry, cosmetic and skin care products and pharmacological products. The substance is also sold “as such” for those who want to include the ingredient in home-made creams and ointments.
The thransesterification process is used to produce bio-fuel from vegetable mass. The process, although different from the saponification, also relies on vegetable fats for bio-fuel production. Apart from the bio-fuel, the thransesterification also results in glycerin. The by-product is known as crude glycerin and has a dark color and a viscous consistency.
European Union created rules which stipulate that at least 5.75% of the vehicle fuel sold at the pump must be biofuel. Therefore the production of glycerin has increased considerably, but is quality is rather poor. Costly procedures need to be undergone in order to purify it and bring it to a usable state that the surplus increases year by year. Currently, only a small percentage of the crude glycerin is refined and re-used in different industries. Most of it is stored in large containers and preserved until an economically viable solution is found.
Synthetic glycerin is the substance obtained from propylene and not from vegetable or animal fats. This chemical procedure is rather complex and expensive, which makes it less popular in modern conditions. Synthetic glycerin is also less appreciated in cosmetic and food industry, therefore the market for it is rather restricted.
Common uses of glycerin
Glycerin is used in various industries, mainly because its capacity of attracting moisture and retaining it for a long period. However, other attributes, such as its great lubrication power and its preservative characteristic have been exploited by different branches of the industry. Here are the most popular uses for this affordable and highly versatile substance.
Glycerin is a humectant and thus has the ability to draw water and retain it. This property has made it extremely popular in the cosmetic industry. It is added in skin care and make-up products for added moisture and for its preservative functions. The substance, once applied on the skin, draws water into the outer layers of the dermis and helps them penetrate the epidermis for an in-depth moisturizing. The skin remains soft to touch and increases its elasticity. The most popular products containing glycerin are soaps, shower gels, face and body creams, scrubs, as well as foundations, BB and CC creams, primers, lipsticks and lip glosses.
The same process of water attraction functions for the hair, so glycerin is added to shampoos, conditioners and hair masks for added moisture and silky-smooth strands.
However, glycerin and glycerin-containing products should not be used in dry areas or during hot summer days, because they tend to dry out the skin/hair. When there is no humidity in the environment, the glycerin will absorb the moisture from the portion onto which is applied, increasing the risk of moist evaporation once on the outer layer of skin/hair. If used in dry areas, it is recommended to be applied with a generous amount of water for an optimal functioning.
Food industry is one of the top glycerin consumers in modern society. In cookies, biscuits and packaged foods, glycerin is used as an additive to preserve the right humidity. The use of glycerin prevents the food from drying and losing its texture. Moist cakes, biscuits that melt in your mouth and soft croissants which make mornings brighter owe their perfect texture to the right amount of glycerin. The fact that they are not so great after leaving the package open for a day or two is also due to glycerin, as the substance will attract extra humidity from the environment into your favorite food, causing it to lose its texture and become too moist or too chewy.
In low fat foods, glycerin is added as a filling or for extra flavor, due to its sweet taste. Also, it has a small glycemic index (3 compared to 65 for sugar), which makes it safe to use for diabetics. Therefore, it is used in foods created especially for people suffering from diabetes and following a low glycemic diet. It must be noted that glycerin has more calories and it is less sweet than sugar, so it is not recommended in losing weight diets.
Glycerin has a syrup-like consistency and a sweet taste, perfect to maintain the viscosity of liqueurs and add them a touch of sweetness. Through series of complex processes which involve condensation and cooling, glycerin can be used to increase the amount of alcohol in a beverage (e.g. fortified wine) or to considerably reduce it and even neutralize it (non-alcoholic beer).
Athletes and people engaged in endurance sportive activities use supplements containing glycerin in order to maximize the water intake and prevent dehydration. The supplement is liquid and can be ingested, as a sweetener or mixed with water in order to prevent useless loss of water. The liquid glycerin can also be applied on the skin to avoid skin dehydration during or after workouts. When applied on the skin, the glycerin must be mixed with water to avoid allergic or toxic reactions caused by the highly concentrated substance. These reactions are rather rare, but prevention is always recommended.
It must be noted that glycerin may have a slightly laxative effect when ingested in large quantities. Bloating, diarrhea and stomach cramps may appear when taking too much glycerin, therefore it is recommended to stick to 50 mg per day or even less, if possible.
The pharmaceutical industry relies heavily on glycerin in order to keep creams and ointments moist and good state. Tinctures and elixirs also may contain glycerin to retain the water, while some medical products rely on it as a preservative. However, glycerin can also be used as a medicine per se. The glycerin suppositories are the most popular relief for constipation, while the liquid glycerin diluted with water can successfully treat psoriasis and other similar skin conditions. It is also used as a vasodilator in angina. Eye conditions and cerebral edema can also benefit from the positive touch of glycerin.
Glycerin is employed in most surprising products and industries, such as cigarettes (to prevent tobacco from crumbling), paper products (including grease-proof paper and food packaging), plastic products (to offer them flexibility) and even dynamite (the famous combination of nitric acid and glycerin). It is also used for lubricating machinery used in the food industry, as it is safe for human ingestion, does not change the food’s taste in case of accidental contamination it and provides a good lubrication for a smooth functioning of the machinery.
Because of its anti-freeze property, glycerin was the first substance to be used in automobile radiator cooling system. In modern cars, its place was taken by ethylene glycol, but combinations of glycerin are still used in some vehicles. In households, glycerin is used for its skin moisturizing properties as well as for its stain removal ability. Home-made detergents and clothing soaps are also added glycerin for added cleaning power.
Side effects of glycerin
There are no major side effects associated with the use of glycerin. Most adults tolerate the substance when applied on the skin. However, glycerin must be diluted when used topically as pure glycerin used directly on skin may cause blisters.
Mild side effects may appear when ingested, but the occurrence is rather rare. Symptoms like thirst, diarrhea, vomiting, nausea, headaches and dizziness have been reported after ingesting glycerin. If experiencing any of the listed symptoms stop the use of glycerin or glycerin containing products. If the symptoms persist, visit a doctor for additional treatment.
There is not sufficient data regarding the use of glycerin during pregnancy and breast-feeding, therefore it is advisable to skip its use during these periods and choose 100% safe alternatives when possible.
Glycerin and the environment
Glycerin is one of the few chemical substances used in industry which do not cause environmental hazards in case of accidental spills. Moreover, it is labelled as a “green” substance, as it is rapidly decomposed by bacteria. There have been less than 50 known accidents which damaged in a small measure the environment; therefore glycerin is considered an environment-friendly substance with a low level of risk for plants and animals.
Water – glycerin is soluble in water and poses very few to no problems when accidentally spilled in the aquatic environment. There have been reported no fish deaths due to glycerin intake. The substance is not toxic in water if the concentration is lower than 5,000 mg/l. Furthermore, there are certain species of microorganisms and algae which can survive concentrations below 10,000 mg/l. However, there have been two cases; one in Iowa and one in Missouri, when the quantity of glycerin spilled were so high that it absorbed all the available oxygen in the decomposition process. This left the fish without air and caused their death shortly after the incident.
Air – glycerin has a very low vapor pressure, which means that it will not heavily dissipate in the air. With a vapor pressure of 1 mmHg at 50 degrees Celsius, glycerin does not pose any threat to air quality.
Soil – tests conducted in the laboratory, in an environment which mimicked soil, showed that glycerin is 92% decomposed in a period of 30 days. The predicted no effect concentration for soil is 92.1mg/kg. This means that any concentration below this level does not affect in any way the soil, the plants and animals which live or feed on that soil.
Glycerin is not flammable and has a low toxicity index. The flora and fauna are very little affected in case of an accidental glycerin spill on soil and on water. The absence of major risks associated to glycerin; make its handling and storage easier than in the case of high risk chemical substances.