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Propylene Glycol and Vegetable Glycerine

Feel free to skip over the wikipedia stuff that was copied, I think its pretty important but is a long read. My comments are at the bottom.


Propylene Glycol

Exact molecular formula is known and posted online
You are smoking C3-H8-O2
Carbon, Hydrogen, Oxygen

Propylene glycol, known also by the systematic name propane-1,2-diol, is an organic compound (a diol alcohol), usually a faintly sweet, and colorless clear viscous liquid that is hygroscopic and miscible with water, acetone, and chloroform.


Propylene glycol contains an asymmetrical carbon atom, so it exists in two stereoisomers. The commercial product is a racemic mixture. Pure optical isomers can be obtained by hydration of optically pure propylene oxide.[2]


Industrially propylene glycol is produced by propylene oxide hydration. Different manufacturers use non-catalytic high-temperature process at 200-220 °C or catalytic route which proceeds at 150-180 °C in presence of ion exchange resin or small amounts of sulfuric acid or alkali. Final products contain 20% 1,2-propanediol, 1.5% of dipropylene glycol and small amount of other polypropylene glycol.[3] Propylene glycol can also be converted from glycerol, a biodiesel byproduct.


Propylene glycol is used:Propylene glycol has properties similar to those of ethylene glycol (monoethylene glycol, or MEG). (Note: propylene glycol may also use the acronym MEG, but as an abbreviation of methyl ethyl glycol.) The industrial norm is to replace ethylene glycol by propylene glycol.


Potential health effects

Eye Causes mild eye irritation. Contact may cause irritation, tearing, and burning pain. Skin Causes moderate skin irritation. Contact with the skin may cause erythema, dryness, and defatting. Ingestion May cause gastrointestinal irritation with nausea, vomiting and diarrhea. Low hazard for usual industrial handling. May cause hemoglobinuric nephrosis. May cause changes in surface EEG. Inhalation Low hazard for usual industrial handling. May cause respiratory tract irritation. Chronic May cause reproductive and fetal effects. Laboratory experiments have resulted in mutagenic effects. Exposure to large doses may cause central nervous system depression. Chronic ingestion may cause lactic acidosis and possible seizures. Cases of propylene glycol poisoning are related to either inappropriate intravenous use or accidental ingestion by children.[5] The oral toxicity of propylene glycol is very low. In one study, rats were provided with feed containing as much as 5% PG over a period of 104 weeks and they showed no apparent ill effects.[6] Because of its low chronic oral toxicity, propylene glycol is generally recognized as safe (GRAS) for use as a direct food additive.
Serious toxicity will occur only at extremely high intakes over a relatively short period of time that result in plasma concentrations of over 4 g/L.[7] Such levels of ingestion would not be possible when consuming reasonable amounts of a food product or dietary supplements containing at most 1 g/kg propylene glycol.
The U.S. Food and Drug Administration (FDA) has determined propylene glycol to be "generally recognized as safe" for use in food, cosmetics, and medicines. Like ethylene glycol, propylene glycol affects the body's chemistry by increasing the amount of acid. Propylene glycol is metabolized into pyruvic acid, which is a normal metabolite in the breakdown of glucose, while ethylene glycol is metabolized into oxalic acid, which is toxic.
The FDA does state that propylene glycol is not approved for use in cat food. The U.S. Food and Drug Administration has determined that propylene glycol in or on cat food has not been shown by adequate scientific data to be safe for use. Use of propylene glycol in or on cat food causes the feed to be adulterated and in violation of the Federal Food, Drug, and Cosmetic Act. 21CFR589.1001
Prolonged contact with propylene glycol is essentially non-irritating to the skin. Undiluted propylene glycol is minimally irritating to the eye, and can produce slight transient conjunctivitis (the eye recovers after the exposure is removed). Exposure to mists may cause eye irritation, as well as upper respiratory tract irritation. Inhalation of the propylene glycol vapors appears to present no significant hazard in ordinary applications. However, limited human experience indicates that inhalation of propylene glycol mists could be irritating to some individuals. Therefore inhalation exposure to mists of these materials should be avoided. Some research has suggested that propylene glycol not be used in applications where inhalation exposure or human eye contact with the spray mists of these materials is likely, such as fogs for theatrical productions or antifreeze solutions for emergency eye wash stations.[8]
Propylene glycol does not cause sensitization and it shows no evidence of being a carcinogen or of being genotoxic.[9][10]
A Clinical Journal of Medicine article states two cases of adult men experiencing psychosis from use of propylene glycol used in phenytoin injection USP. Both patients had to be switched to Cerebyx (Fosphenytoin Sodium) in order to avoid propylene glycol co-solvent.[citation needed]

Allergic reaction

Research has suggested that individuals who cannot tolerate propylene glycol probably experience a special form of irritation, but that they only rarely develop allergic contact dermatitis. Other investigators believe that the incidence of allergic contact dermatitis to propylene glycol may be greater than 2% in patients with eczema.[11]
Patients with vulvodynia and interstitial cystitis may be especially sensitive to propylene glycol. Women struggling with yeast infections may also notice that some OTC creams can cause intense burning.[12]Post menopausal women who require the use of an estrogen cream may notice that brand name creams made with propylene glycol often create extreme, uncomfortable burning along the vulva and perianal area. In these cases, patients can request that a local compounding pharmacy make a "propylene glycol free" cream.

  1. <LI id=cite_note-0>^ Merck Index, 11th Edition, 7868. <LI id=cite_note-1>^ "1,2-Propanediol". ChemIndustry.ru. 1,2-propanediol: chemical product info at CHEMINDUSTRY.RU. Retrieved on 2007-12-28. <LI id=cite_note-2>^ 1,2-propanediol: chemical product info at CHEMINDUSTRY.RU <LI id=cite_note-3>^ Chemical & Engineering News: WHAT'S THAT STUFF? - AIRCRAFT DEICERS <LI id=cite_note-4>^ National Library of Medicine;.Propylene glycol is used in antifreezes Human Toxicity Excerpts: CAS Registry Number: 57-55-6 (1,2-Propylene Glycol). Selected toxicity information from HSDB. 2005. <LI id=cite_note-5>^ Gaunt, IF, Carpanini, FMB, Grasso, P and Lansdown, ABG, Long-term toxicity of propylene glycol in rats, Food and Cosmetics Toxicology, Apr. 1972, 10(2), pages 151 - 162. <LI id=cite_note-6>^ Flanagan RJ;Braithwaite RA;Brown SS;Widdop B;de Wolff FA;. The International Programme on Chemical Safety: Basic Analytical Toxicology. WHO, 1995. <LI id=cite_note-7>^ A Guide to Glycols (File Not Found), page 36. <LI id=cite_note-8>^ 1,2-Dihydroxypropane SIDS Initial Assessment Profile (http://www.chem.unep.ch/irptc/sids/OECDSIDS/57-55-6.pdf), UNEP Publications, SIAM 11, U.S.A, January 23-26, 2001, page 21. <LI id=cite_note-9>^ Title 21, U.S. Code of Federal Regulations. 1999. <LI id=cite_note-10>^ [American Medical Association, Council on Drugs. AMA Drug Evaluations Annual 1994. Chicago, IL: American Medical Association, 1994., p. 1224]
  2. ^ Elizabeth Vliet MD, Screaming To Be Heard: Hormonal Connections That Women Suspect and Doctors Ignore". M. Evans and Company, Inc. New York 1995


Vegetable Glycerine Profile

Exact molecular formula is, after a bit of research....
You are smoking C3-H5-(OH)3
Carbon, Hydrogen, Hydroxide

Botanical Name- Palm derived
Origin- Malaysia
Extraction- Isolated glycerol fats through an Hydrolysis method
Shelf life- 5 years
Notes- Stores well under dark and cool conditions and is extremely volatile to light exposure.
This variety of Glycerine is suitable for food and cosmetic use and is USP standard 99.7% (the rest is water) with no added stabilizers, preservatives and other ingredients.
Color- Clear
Odor/Taste- Flat aroma, very sweet flavor resembling syrup.
Glycerol content- 99.8%
Fatty Acids and Esters- 0.3
Specific Gravity- 1.29
pH- 7
Heavy Metals - <5 ppm
Chlorides- <10 ppm
Chlorinated compounds- <30 ppm
Sulphates- <20 ppm
Moisture- 0.13%
Organic Volatile Impurities- None detected
Diethylene Glycol and related compounds- No trace amounts detected Vegetable Glyceine
Vegetable glycerine comes to us through a very complex and sophisticated method of extraction known as Hydrolysis, and the end product that we refer to as "Vegetable Glycerine" is usually the by-product of another oils production. The basics of this system is that the fats and oils of a raw ingredient (usually palm or coconut oils) are split into crude glycerol fats, under the combined action of water, temperature and pressure. These temperatures can exceed 400° degrees and the material is usually kept under pressure for 20-30 minutes. What is actually occurring is a sort of "counter-flow" where the water absorbs glycerol from the fatty acid phase of the oil production. After this phase this glycerol is isolated and further distilled to give buyers a standard 99% Glycerine product.
Vegetable Glycerine is a clear, colorless, and odorless liquid with an incredibly sweet taste having the consistency of thick syrup. It is used as an agent in cosmetics, toothpaste, shampoos, soaps, herbal remedies, pharmaceuticals, and other household items. Because it is soluble in both, water and alcohol, its versatility is a major benefactor in its purported growth and popularity within the manufacturing sector. It is invaluable as a natural source ingredient with emollient like properties which can soften and soothe the skin and it assists the outer epidermis is retaining moisture. This helps to explain why it is one of the most popular cosmetic additives used today.
Other uses include its solvency action which aides herbalists in extracting botanical properties from plant materials without the use of alcohol. This is especially helpful for those with alcohol sensitivities as most liquid herbal extracts contain alcohol. But given its severely limited shelf life, extracts made from Vegetable Glycerine typically have a shelf life of 14-24 months whereas alcohol extracts can have an extended shelf life of 4-6 years.

There is no wikipedia entry on the substance "vegetable glycerine". But there is one on Glycerine which is where I got structural formula for "vegetable glycerine", which is 99% Glycerine.


Propylene Glycol
You are smoking (unknown synthetic or natural source) C3-H8-O2

Vegetable Glycerine
You are smoking (99.9 percent natural asian palm) C3-H5-(OH)3

Molecular science is hard.

I'm not a scientist.

byproducts of C=Carbon combustion is Carbon dioxide

byproducts of H=Hydrogn combustion is ??? I don't know how just an H molecule reacts to heat when its in the C H O structure and burned. I highly doubt it will produce pure water like hydrogen "fuel", hydrogen fuel does produce pure water using electrolysis or "electrical current" through the fuel, it actually produces steam which is used to power something or charge a battery. Some mixtures can be burned and they implode as well, instead of exploding

The thing is we are not doing this when we vape, we are simply "heating" hydrogen with a heating coil (atomizer). Hydrogen gas is flammable.
Hydrogen/oxygen mixtures are explosives. Go boom! The byproduct probably also contains carbon dioxide.

byproducts of 0=Oxygen combustion, hahahha oxygen expands when heated its a gas, unless its with other stuff, oooops it is with other stuff like hydrogen, then it EXPLODES and releases a byproduct, maybe some chemists can tell us what byproducts are release, im guessing dioxides of varying forms.

OH is an even stranger compound but only possibly found in vegetable glycerin because of the glycerol. Glycerol has OH as its last molecular component. But in essence OH is Oxygen 1 part and Hydrogen 1 part.

From Wiki: Hydroxide is the name for the diatomic anion OH −, consisting of oxygen and hydrogen atoms, usually derived from the dissociation of a base. It is one of the simplest diatomic ions known.

The structure of PG can be an irritant to some people when smoked and could possibly cause liver and kidney damage.

The structure of VG is less of an irritant to some people when smoked because of its natural source, palm plants in asia, but when smoked can also cause liver kidney and damage.

I think the liver/kidney and damage comes from our blood being filtered by our kidneys and liver, they must remove the byproducts of combusting molecules that were inhaled, carbon dioxide (for regular smokes this is also more amounts of carbon hydrogen and oxygen being inhalled because of tobacco plants molecular structure plus all the added chemicals, and also take into account the byproducts of combusting nicotine this adds to the load on kidneys liver).

I think its easily seen LESS cancer causing agents are in e-cigs. Overall the amount of carbon and other molecules needed to produce smoke is also less. ONE entire full smokes worth of plant (tobacco), a full bowl in a pipe per sitting. Overall there is less an amount of Oxygen,Hydrogne,Carbon being combusted.

Overall e-cigs are better for you than tobacco. A huge HUGE reduction in chance of cancer to any body part other than lungs, kidney, liver. A very very signfigant reduction in chance of cancer to lungs, kidney, liver because of the reduction in amount of CHO combusted, plus the lack of extra chemicals.

My last conclusion is the structure of PG could irritate some people and VG could help those people. Both products contain the same elements but in different arrangements.One is natural, one is synthetic.

Do not be so dense as to believe that vape smoke is 100% free of toxins. Its not. The difference is how many, how much and which toxins. For all three of those questions vape smoke beats analogs.

I hope this helps you make a choice on e-cigs and PG over VG

Thanks a lot.
Matt B.

via: E-Cigarette Forum


3 comments for “Propylene Glycol and Vegetable Glycerine”

  1. oooooook here we go. i have taken chemistry classes so i do know what i am talking about. first lets go over the idea that we are burning the PG and the VG. PG has a flash point of 99C what that means is when it gets to 99C it will form an ignitable vapour. if you have an ignition source it will burn but it wont sustain the flame unless it gets to 371C according to the MSDS data i found. VG on the other hand has a flash point of 170C and a burning temp of 425C according to the MSDS data. this means that the odds your actually burning VG in an e cig is remote indeed far more remote then if your vaping PG.

    Now for some chemistry bits. in the E cig atomizer is a very enclosed space even when your taking a drag most of the combustion would be incomplete. that means ALOT of CO(carbon monoxide) and other nasty stuff. you wouldnt actually burn only the glycol you would wind up getting combustion products from the rest of the solution as well. that would include the flavouring the nicotine and it would not taste or smell good at all. oh and before you argue that the heating element constitutes an ignition source. thats true in materials with a flash point of 66C or less. also known as between high and extreme ignition hazards. both PG and VG are in the very low category.

    Posted by James | January 21, 2010, 2:47 pm
  2. Some interesting facts here. I consider myself to be an intelligent person, so I think I can break this all down into layman’s terms.

    The chemical properties of both Propylene Glycol and Vegetable Glycerin are so low in health risks that the FDA allows its use in food products.

    If either of them are completely combusted, the properties become a small risk, due to the change in chemical composition that combustion affects.

    As the knowledgeable person who replied earlier said: Its not possible to fully ignite the compounds in an e cigarette due to a lack of heat.

    So, basically you are inhaling what could potentially be a mild irritant that can cause health problems if inhaled in very large quantities (compared to the amount that is in an e cigarette) over an extended period of time.

    Now think about tobacco cigarettes. They have so many chemicals that no one would want to list them all, or read them. Not only are you inhaling them, you are setting them on fire first. Their byproducts, tar and a concoction of poisons, get stuck to the inside of your lungs and get absorbed into your blood stream. This has to be much worse than a mild irritant with uncommon side effects.

    Basically when switching to E cigarettes, you are trading a slew of poisons for; nicotine (a poison only in large quantities) and 1 or 2 (depending on where you buy/if you mix) nearly harmless chemicals that do not leave remains in your lungs.

    Smokers and smoking advocates: Arguments that E cigarettes are also dangerous are all invalid.

    The bottom line is: E cigarettes are way way way less dangerous to your health and I think everyone who smokes tobacco should convert to them. I’ve been a smoker for 11 years and E cigarettes have changed my life. I couldn’t give up smoking and now I don’t have to. I can be healthy AND happy. Beautiful, isn’t it?

    Thanks, Matt B. You have my support!

    Posted by Melkume | February 2, 2010, 8:48 pm
  3. um……carbon monoxide? no kidding. I haven’t heard anything about this, but you’ve got my attention…

    Posted by Chris | March 15, 2010, 12:43 am

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