View source for Glycerol

{{short description|Chemical compound widely used in food and pharmaceuticals}}{{Redirect|Glycerine|the song by Bush|Glycerine (song)}}{{Use dmy dates|date=August 2024}}{{CS1 config|mode=cs1}}
{{Chembox
| Watchedfields  = changed
| verifiedrevid  = 464392960
| Name           = Glycerol
| ImageFile1     = Glycerin_Skelett.svg
| ImageName1     = Glycerol
| ImageClass1    = skin-invert-image
| ImageFileL2    = Glycerol-3D-balls.png
| ImageNameL2    = Ball-and-stick model of glycerol
| ImageFileR2    = Glycerol-3D-vdW.png
| ImageNameR2    = Space-filling model of glycerol
| ImageFile3     = Sample of Glycerine.jpg
| ImageName3     = Sample of glycerine
| PIN            = Propane-1,2,3-triol<ref>{{cite book |author=[[International Union of Pure and Applied Chemistry]] |date=2014 |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 |publisher=[[Royal Society of Chemistry|The Royal Society of Chemistry]] |pages=690 |doi=10.1039/9781849733069 |isbn=978-0-85404-182-4}}</ref>
| OtherNames     = {{Unbulleted list
  | 1,2,3-Trioxypropane
  | 1,2,3-Trihydroxypropane
  | 1,2,3-Propanetriol
  }}
| Section1       = {{Chembox Identifiers
|IUPHAR_ligand = 5195
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = PDC6A3C0OX
|KEGG_Ref = {{keggcite|correct|kegg}}
|KEGG = D00028
|InChI = 1/C3H8O3/c4-1-3(6)2-5/h3-6H,1-2H2
|InChIKey = PEDCQBHIVMGVHV-UHFFFAOYAF
|ChEMBL_Ref = {{ebicite|correct|EBI}}
|ChEMBL = 692
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/C3H8O3/c4-1-3(6)2-5/h3-6H,1-2H2
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = PEDCQBHIVMGVHV-UHFFFAOYSA-N
|CASNo_Ref = {{cascite|correct|CAS}}
|CASNo = 56-81-5
|PubChem = 753
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|ChemSpiderID = 733
|DrugBank_Ref = {{drugbankcite|correct|drugbank}}
|DrugBank = DB04077
|ChEBI = 17754
|ChEBI_Ref = {{ebicite|correct|EBI}}
|SMILES = OCC(O)CO
}}
| Section2       = {{Chembox Properties
|C=3 | H=8 | O=3
|Appearance = Colorless [[hygroscopic]] liquid
|Odor = Odorless
|Density = 1.261 g/cm<sup>3</sup>
|Viscosity = 1.412 Pa·s (20&nbsp;°C)<ref name="Viscosity of Glycerol and its Aqueous Solutions">{{cite journal |last1= Segur |first1= J. B. |last2= Oberstar |first2= H. E. |doi= 10.1021/ie50501a040 |title= Viscosity of Glycerol and Its Aqueous Solutions |journal= Industrial & Engineering Chemistry |volume= 43 |issue= 9 |pages= 2117–2120 |year= 1951 }}</ref>
|MeltingPtC = 17.8
|BoilingPtC = 290
|BoilingPt_ref = <ref>{{cite book |editor= Lide, D. R. |title= CRC Handbook of Data on Organic Compounds |edition= 3rd |publisher= CRC Press |location= Boca Raton, FL |year= 1994 |page= 4386}}</ref>
|RefractIndex = 1.4746
|VaporPressure = {{cvt|0.003|mmHg|Pa}} at 50&nbsp;°C<ref name=PGCH/>
|Solubility = miscible<ref name=PGCH/>
|MagSus = {{val|-57.06e-6|u=cm<sup>3</sup>/mol}}
|LogP = −2.32<ref name="chemsrc">{{Cite web|url=https://www.chemsrc.com/en/cas/56-81-5_401679.html|title=glycerin_msds|access-date=7 May 2018|archive-date=8 March 2020|archive-url=https://web.archive.org/web/20200308030040/https://www.chemsrc.com/en/cas/56-81-5_401679.html|url-status=live}}</ref>
}}
| Section3       = {{Chembox Pharmacology
|ATCCode_prefix = A06
|ATCCode_suffix = AG04
|ATC_Supplemental = {{ATC|A06|AX01}}, {{ATCvet|A16|QA03}}
}}
| Section4       = {{Chembox Hazards
|ExternalSDS = {{usurped|1=[https://web.archive.org/web/20110505085357/https://www.jtbaker.com/msds/englishhtml/g4774.htm JT Baker ver. 2008 archive]}}
|NFPA-H = 1
|NFPA-F = 1
|NFPA-R = 0
|FlashPt = {{convert|160|C|F K}} (closed cup)<br /> {{convert|176|C|F K}} (open cup)
|PEL = TWA 15&nbsp;mg/m<sup>3</sup> (total)<br /> TWA 5&nbsp;mg/m<sup>3</sup> (resp)<ref name=PGCH>{{PGCH|0302}}</ref>
|IDLH = N.D.<ref name=PGCH/>
|REL = None established<ref name=PGCH/>
}}
}}

'''Glycerol''' ({{IPAc-en|ˈ|g|l|ɪ|s|ə|r|ɒ|l}})<ref>{{cite web|url=https://www.oxforddictionaries.com/definition/english/glycerol|title=glycerol – Definition of glycerol in English by Oxford Dictionaries|website=Oxford Dictionaries – English|access-date=21 February 2022|archive-date=21 June 2016|archive-url=https://web.archive.org/web/20160621205507/http://www.oxforddictionaries.com/definition/english/glycerol|url-status=dead}}</ref> is a simple [[triol]] compound. It is a colorless, odorless, sweet-tasting, [[viscous]] liquid. The glycerol backbone is found in [[lipid]]s known as [[glyceride]]s. It is also widely used as a sweetener in the food industry and as a [[humectant]] in [[pharmaceutical formulation]]s. Because of its three [[hydroxyl group]]s, glycerol is [[miscible]] with [[water]] and is [[Hygroscopy|hygroscopic]] in nature.<ref name="Ullmann"/>

Modern use of the word '''glycerine''' (alternatively spelled '''glycerin''') refers to commercial preparations of less than 100% purity, typically 95% glycerol.<ref>{{cite web|url= https://www.echemi.com/cms/1795050.html |title=Is There any Difference Between Glycerin and Glycerol?|website=Oxford Dictionaries – English|date=9 April 2024|access-date=20 October 2024}}</ref>

==Structure==
Although [[chirality|achiral]], glycerol is [[prochirality|prochiral]] with respect to reactions of one of the two primary alcohols. Thus, in substituted derivatives, the [[Glycerophospholipid#Nomenclature and stereochemistry|stereospecific numbering]] labels the molecule with a ''sn''- prefix before the stem name of the molecule.<ref>{{cite journal |last=Hirschmann|first=H.|date=1960-10-01|title=The Nature of Substrate Asymmetry in Stereoselective Reactions|journal=Journal of Biological Chemistry|volume=235|issue=10|pages=2762–2767|doi=10.1016/S0021-9258(18)64537-5|pmid=13714619|doi-access=free}}</ref><ref>{{cite journal |date=1967-09-01|title=IUPAC-IUB Commission on Biochemical Nomenclature (CBN)|journal=European Journal of Biochemistry|volume=2|issue=2|pages=127–131|doi=10.1111/j.1432-1033.1967.tb00116.x|pmid=6078528|doi-access=}}</ref><ref name="pmid29301208">{{cite journal | vauthors=Alfieri A, Imperlini E, Nigro E, Vitucci D, Orrù S, Daniele A, Buono P, Mancini A | title=Effects of Plant Oil Interesterified Triacylglycerols on Lipemia and Human Health | journal= [[International Journal of Molecular Sciences]] | volume=19 | issue=1 | pages=E104 | year=2017 | doi= 10.3390/ijms19010104 |  pmc =5796054 | pmid = 29301208 | doi-access=free}}</ref>

==Production==
===Natural sources===
Glycerol is generally obtained from plant and animal sources where it occurs in [[triglyceride]]s, [[ester]]s of glycerol with long-chain [[carboxylic acids]]. The [[hydrolysis]], [[saponification]], or [[transesterification]] of these triglycerides produces glycerol as well as the fatty acid derivative:
<div style="display: flex; max-width: 100%; overflow-x: auto">
{{Biochem reaction subunit |compound=Triglyceride |class=skin-invert-image|image=Fat_structural_formulae_V3.svg |imagesize=150px}}
{{Biochem reaction subunit |direction=forward |title=3 [[NaOH]] / {{H2O-nl}} |title_lower={{abbr|Δ|heating}}}}
{{Biochem reaction subunit |n=3 |compound=soap |class=skin-invert-image|image=General sodium carboxylate.svg}}
{{Biochem reaction subunit |compound=glycerol |class=skin-invert-image|image=Glycerine Structural Formula V1.svg}}
</div>
Triglycerides can be saponified with [[sodium hydroxide]] to give glycerol and fatty sodium salt or [[soap]].

Typical plant sources include [[soybeans]] or [[Arecaceae|palm]]. Animal-derived [[tallow]] is another source. From 2000 to 2004, approximately 950,000 tons per year were produced in the United States and Europe; 350,000 tons of glycerol were produced in the U.S. alone.<ref>{{cite web |title= A Glycerin Factor |author= Nilles, Dave |url= https://www.biodieselmagazine.com/article.jsp?article_id=377 |publisher= Biodiesel Magazine |year= 2005 |access-date= 21 February 2022 |archive-date= 8 November 2007 |archive-url= https://web.archive.org/web/20071108114027/http://www.biodieselmagazine.com/article.jsp?article_id=377 |url-status= live }}</ref> Since around 2010, there is a large surplus of glycerol as a byproduct of [[biofuel]], enforced for example by [[Directive on the Promotion of the use of biofuels and other renewable fuels for transport|EU directive 2003/30/EC]] that required 5.75% of petroleum fuels to be replaced with biofuel sources across all [[Member state of the European Union|member states]].<ref name="Ullmann">{{cite encyclopedia |encyclopedia= Ullmann's Encyclopedia of Industrial Chemistry |last1= Christoph |first1= Ralf |last2= Schmidt |first2= Bernd |last3= Steinberner |first3= Udo |last4= Dilla |first4= Wolfgang |last5= Karinen |first5= Reetta |year= 2006 |doi= 10.1002/14356007.a12_477.pub2 |chapter= Glycerol |isbn= 3527306730}}</ref>
Crude glycerol produced from triglycerides is of variable quality, with a selling price as low as US$0.02–0.05 per kilogram in 2011.<ref>{{cite journal |last1 = San Kong |first1 = Pei |last2 = Kheireddine Aroua |first2 = Mohamed |last3 = Ashri Wan Daud |first3 = Wan Mohd |year = 2016 |title = Conversion of crude and pure glycerol into derivatives: A feasibility evaluation |journal = Renewable and Sustainable Energy Reviews |volume = 63 |pages = 533–555 |doi = 10.1016/j.rser.2016.05.054 |bibcode = 2016RSERv..63..533K }}</ref> It can be purified in a rather expensive process by treatment with [[activated carbon]] to remove organic impurities, alkali to remove unreacted glycerol esters, and [[ion exchange]] to remove salts. High purity glycerol (greater than 99.5%) is obtained by multi-step distillation; a [[vacuum chamber]] is necessary due to its high boiling point (290&nbsp;°C).<ref name=Ullmann/>

Consequently, glycerol recycling is more of a challenge than its production, for instance by conversion to glycerol carbonate<ref>{{Cite journal |last1=Das |first1=Arpita |last2=Kodgire |first2=Pravin |last3=Li |first3=Hu |last4=Basumatary |first4=Sanjay |last5=Baskar |first5=Gurunathan |last6=Rokhum |first6=Samuel Lalthazuala |date=2023 |title=Recent Advances in Conversion of Glycerol: A Byproduct of Biodiesel Production to Glycerol Carbonate |journal=Journal of Chemistry |language=en |volume=2023 |issue=1 |pages=8730221 |doi=10.1155/2023/8730221 |doi-access=free |issn=2090-9071}}</ref> or to synthetic precursors, such as [[acrolein]] and epichlorohydrin.<ref>{{cite journal |title= Glycerol|last= Yu|first= Bin|journal= Synlett|volume= 25|issue= 4|pages= 601–602|doi= 10.1055/s-0033-1340636|year= 2014|doi-access= free}}</ref>

===Synthetic glycerol===
Although more expensive than production from plant or animal triglycerides, glycerol can be synthesized by various routes.  During [[World War II]], synthetic glycerol processes became a national defense priority because it is a precursor to [[nitroglycerine]]. Epichlorohydrin is the most important precursor. [[Chlorination reaction|Chlorination]] of propylene gives [[allyl chloride]], which is oxidized with [[hypochlorite]] to [[dichlorohydrin]], which reacts with a strong base to give [[epichlorohydrin]]. Epichlorohydrin can be hydrolyzed to glycerol. [[Chlorine]]-free processes from propylene include the synthesis of glycerol from [[acrolein]] and [[propylene oxide]].<ref name="Ullmann" />
: [[File:Synthetic routes to glycerol.png|class=skin-invert-image|600px]]

==Applications==
===Food industry===
In food and beverages, glycerol serves as a [[humectant]], [[solvent]], and [[sweetener]], and may help [[Food preservative|preserve foods]]. It is also used as filler in commercially prepared [[low-fat]] foods (e.g., [[cookie]]s), and as a [[thickening agent]] in [[liqueur]]s. Glycerol and water are used to preserve certain types of plant leaves.<ref>{{cite journal |url= https://extension.umd.edu//sites/extension.umd.edu/files/_images/programs/hgic/Publications/non_HGIC_FS/FS556.pdf |title= Preserving flowers and leaves |last= Gouin |first= Francis R. |year= 1994 |journal= Maryland Cooperative Extension Fact Sheet |volume= 556 |pages= 1–6 |access-date= 20 January 2018 |archive-date= 21 January 2018 |archive-url= https://web.archive.org/web/20180121072119/https://extension.umd.edu//sites/extension.umd.edu/files/_images/programs/hgic/Publications/non_HGIC_FS/FS556.pdf |url-status= live }}</ref><!--<ref>{{cite web |title= Preserving flowers and decorative foliages with glycerin and dye |author= Stevens, Alan |url= https://www.ksre.ksu.edu/library/hort2/mf2446.pdf }}{{dead link |date=October 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>--> As a [[sugar substitute]], it has approximately 27 [[Food energy|kilocalories]] per [[teaspoon]] (sugar has 20) and is 60% as [[Sweetness|sweet]] as [[sucrose]].{{Citation needed|date=May 2025}} It does not feed the [[bacteria]] that form [[dental plaque]] and cause [[dental cavities]].{{citation needed |date=October 2016}} As a [[food additive]], glycerol is labeled as [[E number]] E422. It is added to [[Icing (food)|icing]] (frosting) to prevent it from setting too hard.

As used in foods, glycerol is categorized by the U.S. [[Academy of Nutrition and Dietetics]] as a [[carbohydrate]]. The U.S. [[Food and Drug Administration]] (FDA) carbohydrate designation includes all caloric [[macronutrient]]s excluding protein and fat. Glycerol has a caloric density similar to table sugar, but a lower [[glycemic index]] and different [[metabolic pathway]] within the body.

It is also recommended as an additive when polyol sweeteners such as [[erythritol]] and [[xylitol]] are used, as its heating effect in the mouth will counteract these sweeteners' cooling effect.<ref>{{cite web |title= Functional Food Design Rules |author= Nikolov, Ivan |date= 20 April 2014 |url= https://www.ivannikolov.com/functional-food-design-rules-part-2/ |access-date= 21 February 2022 |archive-date= 30 April 2021 |archive-url= https://web.archive.org/web/20210430030741/https://ivannikolov.com/functional-food-design-rules-part-2/ |url-status= live }}</ref>

===Medical===
[[File:Glycerin bottle.jpg|thumb|A bottle of glycerin purchased at a pharmacy]]
[[File:Gleitmittel Personal Lubricants.jpg|thumb|Personal lubricants commonly contain glycerol]]
[[File:Dollop of hair gel.jpg|thumb|Glycerol is an ingredient in products such as hair gel]]
[[File:Glycerin suppositories.jpg|thumb|right|Glycerol suppositories used as laxatives]]

Glycerol is used in [[medicine|medical]], [[pharmaceutical]] and [[personal care]] preparations, often as a means of improving smoothness, providing [[lubrication]], and as a [[humectant]].

[[Ichthyosis]] and [[xerosis]] have been relieved by the topical use of glycerin.<ref>{{cite book|title=Ichthyosis: New Insights for the Healthcare Professional|date=22 July 2013|publisher=[[ScholarlyEditions]]|language=en|isbn=9781481659666|page=22}}</ref><ref name="LebwohlHeymann2017">{{cite book|title=Treatment of Skin Disease E-Book: Comprehensive Therapeutic Strategies|date=19 September 2017|publisher=Elsevier Health Sciences|language=en|isbn=9780702069130 |author=Mark G. Lebwohl |author2=Warren R. Heymann |author3=John Berth-Jones |author4=Ian Coulson}}</ref> It is found in allergen [[Immunotherapy|immunotherapies]], [[cough syrup]]s, [[elixir]]s and [[expectorant]]s, [[toothpaste]], [[mouthwash]]es, [[skin care]] products, shaving cream, [[hair care]] products, [[soap]]s, and water-based [[personal lubricant]]s. In solid dosage forms like tablets, glycerol is used as a tablet holding agent. For human consumption, glycerol is classified by the FDA among the [[sugar alcohol]]s as a caloric macronutrient. Glycerol is also used in [[blood bank]]ing to preserve [[red blood cell]]s prior to freezing.<ref>{{cite book
| last = Lagerberg
| first = Johan W.
| chapter = Cryopreservation of Red Blood Cells
| title = Cryopreservation and Freeze-Drying Protocols
| series = [[Methods in Molecular Biology]]
| publisher = [[Humana Press]]
| year = 2015
| volume = 1257
| pages = 353–367
| doi = 10.1007/978-1-4939-2193-5_17
| pmid = 25428017
| isbn = 978-1-4939-2192-8
}}</ref>

Taken rectally, glycerol functions as a [[laxative]] by irritating the anal mucosa and inducing a [[Osmotic laxative|hyperosmotic effect]],<ref>{{cite web |url= https://www.drugs.com/cdi/glycerin-enema.html |title= Glycerin Enema |publisher= Drugs.com |access-date= 17 November 2012 |archive-date= 6 November 2012 |archive-url= https://web.archive.org/web/20121106235146/http://www.drugs.com/cdi/glycerin-enema.html |url-status= live }}</ref> expanding the [[Large intestine|colon]] by drawing water into it to induce [[peristalsis]] resulting in [[Defecation|evacuation]].<ref>{{cite web |url=https://www.cancer.gov/publications/dictionaries/cancer-drug/def/glycerin-enema |title=glycerin enema |work=NCI Drug Dictionary |publisher=[[National Cancer Institute]] |access-date=2019-05-02 |date=2 February 2011 |archive-date=2 May 2019 |archive-url=https://web.archive.org/web/20190502220442/https://www.cancer.gov/publications/dictionaries/cancer-drug/def/glycerin-enema |url-status=live }}</ref> It may be administered undiluted either as a [[suppository]] or as a small-volume (2–10&nbsp;ml) [[enema]]. Alternatively, it may be administered in a dilute solution, such as 5%, as a high-volume enema.<ref>{{Citation |author=E. Bertani |author2=A. Chiappa |author3=R. Biffi |author4=P. P. Bianchi |author5=D. Radice |author6=V. Branchi |author7=S. Spampatti |author8=I. Vetrano |author9=B. Andreoni | title = Comparison of oral polyethylene glycol plus a large volume glycerine enema with a large volume glycerine enema alone in patients undergoing colorectal surgery for malignancy: a randomized clinical trial  | journal = Colorectal Disease | volume = 13 | issue = 10  | pages = e327–e334 | year = 2011 | pmid = 21689356  | doi = 10.1111/j.1463-1318.2011.02689.x  | s2cid = 32872781}}</ref>

Taken orally (often mixed with fruit juice to reduce its sweet taste), glycerol can cause a rapid, temporary decrease in the [[Intraocular pressure|internal pressure of the eye]]. This can be useful for the initial emergency treatment of severely elevated eye pressure.<ref>{{cite web |url= https://www.mayoclinic.com/health/drug-information/DR601713 |title= Glycerin (Oral Route) |publisher= Mayo Foundation for Medical Education and Research |access-date= 17 November 2012 |archive-date= 27 November 2012 |archive-url= https://web.archive.org/web/20121127150445/http://www.mayoclinic.com/health/drug-information/DR601713 |url-status= live }}</ref>

In 2017, researchers showed that the probiotic ''[[Limosilactobacillus reuteri]]'' bacteria can be supplemented with glycerol to enhance its production of antimicrobial substances in the human gut. This was confirmed to be as effective as the antibiotic [[vancomycin]] at inhibiting ''[[Clostridioides difficile]]'' infection without having a significant effect on the overall microbial composition of the gut.<ref>{{Cite journal |last1=Spinler |first1=Jennifer K. |last2=Auchtung |first2=Jennifer |last3=Brown |first3=Aaron |last4=Boonma |first4=Prapaporn |last5=Oezguen |first5=Numan |last6=Ross |first6=Caná L. |last7=Luna |first7=Ruth Ann |last8=Runge |first8=Jessica |last9=Versalovic |first9=James |last10=Peniche |first10=Alex |last11=Dann |first11=Sara M. |date=October 2017 |title=Next-Generation Probiotics Targeting ''Clostridium difficile'' through Precursor-Directed Antimicrobial Biosynthesis |journal=Infection and Immunity |volume=85 |issue=10 |pages=e00303–17 |doi=10.1128/IAI.00303-17 |issn=1098-5522 |pmc=5607411 |pmid=28760934}}</ref>

Glycerol has also been incorporated as a component of [[bio-ink]] formulations in the field of [[3D bioprinting|bioprinting]].<ref>{{Cite journal|last1=Atala|first1=Anthony|last2=Yoo|first2=James J.|last3=Carlos Kengla|last4=Ko|first4=In Kap|last5=Lee|first5=Sang Jin|last6=Kang|first6=Hyun-Wook|date=March 2016|title=A 3D bioprinting system to produce human-scale tissue constructs with structural integrity|journal=Nature Biotechnology|volume=34|issue=3|pages=312–319|doi=10.1038/nbt.3413|pmid=26878319|s2cid=9073831|issn=1546-1696}}</ref> The glycerol content acts to add viscosity to the bio-ink without adding large protein, saccharide, or glycoprotein molecules.

===Botanical extracts===
When utilized in tincture method extractions, specifically as a 10% solution, glycerol prevents tannins from precipitating in ethanol extracts of plants ([[tincture]]s). It is also used as an "alcohol-free" alternative to ethanol as a solvent in preparing herbal extractions. It is less extractive when utilized in a standard tincture methodology. Alcohol-based tinctures can also have the alcohol removed and replaced with glycerol for its preserving properties. Such products are not "alcohol-free" in a scientific or FDA regulatory sense, as glycerol contains three hydroxyl groups. [[Fluid extract]] manufacturers often extract herbs in hot water before adding glycerol to make [[glycerite]]s.<ref>{{cite journal |last1=Long |first1=Walter S. |title=The Composition of Commercial Fruit Extracts |journal=Transactions of the Kansas Academy of Science |date=14 January 1916 |volume=28 |pages=157–161 |doi=10.2307/3624347 |jstor=3624347 }}</ref><ref>[https://www.newhope.com/nutritionsciencenews/NSN_backs/Apr_99/backtalk.cfm Does alcohol belong in herbal tinctures?] {{webarchive |url=https://web.archive.org/web/20071012040650/https://newhope.com/nutritionsciencenews/NSN_backs/Apr_99/backtalk.cfm |date=12 October 2007}} newhope.com</ref>

When used as a primary "true" alcohol-free botanical extraction solvent in non-tincture based methodologies, glycerol has been shown to possess a high degree of extractive versatility for botanicals including removal of numerous constituents and complex compounds, with an extractive power that can rival that of alcohol and water–alcohol solutions.<ref>{{cite web|url = https://www.aciscience.org/docs/Glycerine_-_an_overview.pdf |website =aciscience.org|archive-url= https://web.archive.org/web/20190601153919/http://www.aciscience.org/docs/glycerine_-_an_overview.pdf |archive-date=1 June 2019 |title = Glycerine: An Overview |publisher = The Soap and Detergent Association|date = 1990|url-status = live}}</ref> That glycerol possesses such high extractive power assumes it is utilized with dynamic (critical) methodologies as opposed to standard passive "tincturing" methodologies that are better suited to alcohol. Glycerol does not denature or render a botanical's constituents inert as alcohols ([[ethanol]], [[methanol]], and so on) do. Glycerol is a stable preserving agent for botanical extracts that, when utilized in proper concentrations in an extraction solvent base, does not allow inverting or [[Redox|reduction-oxidation]] of a finished extract's constituents, even over several years.{{citation needed |date=September 2014}} Both glycerol and ethanol are viable preserving agents. Glycerol is [[bacteriostatic]] in its action, and ethanol is bactericidal in its action.<ref>Lawrie, James W. (1928) ''Glycerol and the glycols – production, properties and analysis''. The Chemical Catalog Company, Inc., New York, NY.</ref><ref>Leffingwell, Georgia and Lesser, Miton (1945) ''Glycerin – its industrial and commercial applications''. Chemical Publishing Co., Brooklyn, NY.{{page needed |date=December 2019}}</ref><ref>''The manufacture of glycerol'' – Vol. III (1956). The Technical Press, LTD., London.{{page needed |date=December 2019}}</ref>

===Electronic cigarette liquid===
[[File:E-Cigarette-Electronic Cigarette-E-Cigs-E-Liquid-Vaping-Cloud Chasing (16348040092).jpg|thumb|Glycerin is often used in [[electronic cigarettes]] to create the vapor]]
Glycerin, along with [[propylene glycol]], is a common component of [[construction of electronic cigarettes#E-cigarette liquid|e-liquid]], a solution used with electronic vaporizers ([[electronic cigarettes]]). This glycerol is heated with an atomizer (a heating coil often made of [[Kanthal (alloy)|Kanthal]] wire), producing the [[aerosol]] that delivers [[nicotine]] to the user.<ref>{{cite book|last1=Dasgupta|first1=Amitava|last2=Klein|first2=Kimberly|title=Antioxidants in Food, Vitamins and Supplements: Prevention and Treatment of Disease|date=2014|publisher=Academic Press|isbn=9780124059177|chapter-url=https://books.google.com/books?id=5iiSAgAAQBAJ&q=propylene%20glycol%20electronic%20cigarettes&pg=PA67|access-date=16 August 2017|chapter=4.2.5 Are Electronic Cigarettes Safe?|archive-date=16 April 2021|archive-url=https://web.archive.org/web/20210416173028/https://books.google.com/books?id=5iiSAgAAQBAJ&q=propylene%20glycol%20electronic%20cigarettes&pg=PA67|url-status=live}}</ref>

===Antifreeze===
{{Main|Antifreeze}}
Like [[ethylene glycol]] and propylene glycol, glycerol is a non-ionic [[kosmotropic|kosmotrope]] that forms strong hydrogen bonds with water molecules, competing with water-water [[hydrogen bonds]]. This interaction disrupts the formation of ice. The minimum freezing point temperature is about {{convert|−36|F|C|order=flip}} corresponding to 70% glycerol in water.

Glycerol was historically used as an anti-freeze for automotive applications before being replaced by ethylene glycol, which has a lower freezing point. While the minimum freezing point of a glycerol-water mixture is higher than an ethylene glycol-water mixture, glycerol is not toxic and is being re-examined for use in automotive applications.<ref>{{cite book |last1= Hudgens |first1= R. Douglas |title= SAE Technical Paper Series |volume= 1 |last2= Hercamp |first2= Richard D. |last3= Francis |first3= Jaime |last4= Nyman |first4= Dan A. |last5= Bartoli |first5= Yolanda |year= 2007 |doi= 10.4271/2007-01-4000 |chapter= An Evaluation of Glycerin (Glycerol) as a Heavy Duty Engine Antifreeze/Coolant Base }}</ref><ref>[https://www.astmnewsroom.org/default.aspx?pageid=2115&year=2010&category=Standards%2FTechnical Proposed ASTM Engine Coolant Standards Focus on Glycerin] {{Webarchive|url=https://web.archive.org/web/20170914125754/http://www.astmnewsroom.org/default.aspx?pageid=2115&year=2010&category=Standards%2FTechnical |date=14 September 2017}}. Astmnewsroom.org. Retrieved on 15 August 2012</ref>

In the laboratory, glycerol is a common component of solvents for [[enzymatic]] [[reagents]] stored at temperatures below {{convert|0|C|F}} due to the [[Freezing-point depression|depression of the freezing temperature]]. It is also used as a [[cryoprotectant]] where the glycerol is dissolved in water to reduce damage by ice crystals to laboratory organisms that are stored in frozen solutions, such as [[fungi]], [[bacteria]], [[nematode]]s, and mammalian embryos. Some organisms like the [[moor frog]] produce glycerol to survive freezing temperatures during hibernation.<ref name="Shekhovtsov-2022">{{Cite journal |last1=Shekhovtsov |first1=Sergei V. |last2=Bulakhova |first2=Nina A. |last3=Tsentalovich |first3=Yuri P. |last4=Zelentsova |first4=Ekaterina A. |last5=Meshcheryakova |first5=Ekaterina N. |last6=Poluboyarova |first6=Tatiana V. |last7=Berman |first7=Daniil I. |date=January 2022 |title=Metabolomic Analysis Reveals That the Moor Frog ''Rana arvalis'' Uses Both Glucose and Glycerol as Cryoprotectants |journal=Animals |language=en |volume=12 |issue=10 |pages=1286 |doi=10.3390/ani12101286 |issn=2076-2615 |pmc=9137551 |pmid=35625132 |doi-access=free}}</ref>

===Chemical intermediate===
Glycerol is used to produce a variety of useful derivatives.

[[Nitration]] gives [[nitroglycerin]], an essential ingredient of various explosives such as [[dynamite]], [[gelignite]], and propellants like [[cordite]]. Nitroglycerin under the name glyceryl trinitrate (GTN) is commonly used to relieve [[angina pectoris]], taken in the form of [[sub-lingual]] tablets, patches, or as an [[aerosol]] spray.

Trifunctional [[polyether polyol]]s are produced from glycerol and [[propylene oxide]].

Oxidation of glycerol affords [[mesoxalic acid]].<ref name="ciri2">{{cite journal |last1 = Ciriminna |first1 = Rosaria |last2 = Pagliaro |first2 = Mario |year = 2003 |title = One-Pot Homogeneous and Heterogeneous Oxidation of Glycerol to Ketomalonic Acid Mediated by TEMPO |journal = Advanced Synthesis & Catalysis |volume = 345 |issue = 3 |pages = 383–388 |doi = 10.1002/adsc.200390043}}</ref> Dehydrating glycerol affords [[hydroxyacetone]].

Chlorination of glycerol gives the [[1-chloropropane-2,3-diol]]:
: {{chem2|HOCH(CH2OH)2  +  HCl ->  HOCH(CH2Cl)(CH2OH)  +  H2O}}
The same compound can be produced by hydrolysis of epichlorohydrin.<ref>{{cite journal |doi=10.1021/cr5004002 |title=Glycerol Ether Synthesis: A Bench Test for Green Chemistry Concepts and Technologies |date=2015 |last1=Sutter |first1=Marc |last2=Silva |first2=Eric Da |last3=Duguet |first3=Nicolas |last4=Raoul |first4=Yann |last5=Métay |first5=Estelle |last6=Lemaire |first6=Marc |journal=Chemical Reviews |volume=115 |issue=16 |pages=8609–8651 |pmid=26196761 |url=https://hal.archives-ouvertes.fr/hal-01312971/file/ChemRev_2015_115_8609-8651.pdf }}</ref>

Epoxidation by reaction with [[epichlorohydrin]] and a [[Lewis acid]] yields [[Glycerol triglycidyl ether]].<ref>{{Cite journal |last=Crivello |first=James V. |date=2006 |title=Design and synthesis of multifunctional glycidyl ethers that undergo frontal polymerization |url=https://doi.org/10.1002/pola.21761 |journal=Journal of Polymer Science Part A: Polymer Chemistry |volume=44 |issue=21 |pages=6435–6448 |doi=10.1002/pola.21761 |bibcode=2006JPoSA..44.6435C |issn=0887-624X|url-access=subscription }}</ref><ref>{{Cite patent|country=US|pubdate=1992-11-10|assign1=[[Novartis#Ciba-Geigy|Ciba-Geigy Corp.]]|number=5162547|title=Process for the preparation of glycidyl ethers|=|inventor1-last=Roth|inventor1-first=Martin|inventor2-last=Wolleb|inventor2-first=Heinz|inventor3-last=Truffer|inventor3-first=Marc-Andre}}</ref>

===Vibration damping===
Glycerol is used as fill for [[pressure gauge]]s to damp vibration. External vibrations, from compressors, engines, pumps, etc., produce [[harmonic oscillation|harmonic]] vibrations within [[Bourdon gauge]]s that can cause the needle to move excessively, giving inaccurate readings. The excessive swinging of the needle can also damage internal gears or other components, causing premature wear. Glycerol, when poured into a gauge to replace the air space, reduces the harmonic vibrations that are transmitted to the needle, increasing the lifetime and reliability of the gauge.<ref>''Pneumatic Systems: Principles and Maintenance'' by S. R. Majumdar.  McGraw-Hill, 2006, p. 74 {{ISBN?}}</ref>

===Niche uses===
====Entertainment industry====
Glycerol is used by set decorators when filming scenes involving water to prevent an area meant to look wet from drying out too quickly.<ref>{{cite web |last1=Hawthorne |first1=Amy |title=Chemicals in Film: 20th Century Fox orders Products |url=http://www.reagent.co.uk/blog/chemicals-in-film-20th-century-fox-orders-products/ |website=ReAgent |archive-url=https://web.archive.org/web/20150929170803/http://www.reagent.co.uk/blog/chemicals-in-film-20th-century-fox-orders-products/ |archive-date=2015-09-29 |date=2015-05-04 |url-status=dead}}</ref>

Glycerine is also used in the generation of [[theatrical smoke and fog]] as a component of the fluid used in [[fog machine]]s as a replacement for [[glycol]], which has been shown to be an irritant if exposure is prolonged.

====Ultrasonic couplant====
Glycerol can be sometimes used as replacement for water in [[ultrasonic testing]], as it has favourably higher [[acoustic impedance]] (2.42&nbsp;MRayl versus 1.483&nbsp;MRayl for water) while being relatively safe, non-toxic, non-corrosive and relatively low cost.<ref>[https://www.nde-ed.org/GeneralResources/MaterialProperties/UT/ut_matlprop_liquids.htm Acoustic Properties for Liquids] {{Webarchive|url=https://web.archive.org/web/20161027055440/https://www.nde-ed.org/GeneralResources/MaterialProperties/UT/ut_matlprop_liquids.htm |date=27 October 2016}} nde-ed.org</ref>

===Internal combustion fuel===
Glycerol is also used to power diesel generators supplying electricity for the [[FIA]] [[Formula E]] series of electric race cars.<ref>{{usurped|1=[https://web.archive.org/web/20150212152226/https://www.fiaformulae.com/en/news/2014/september/formula-e-uses-pollution-free-glycerine-to-charge-cars.aspx Formula E uses pollution-free glycerine to charge cars]}}. fiaformulae.com. 13 September 2014</ref>

===Research on additional uses===
Research continues into potential [[value-added]] products of glycerol obtained from biodiesel production.<ref>{{cite journal |doi= 10.1002/ep.10225 |title= The glycerin glut: Options for the value-added conversion of crude glycerol resulting from biodiesel production |year= 2007 |last1= Johnson |first1= Duane T. |last2= Taconi |first2= Katherine A. |journal= Environmental Progress |volume= 26 |issue= 4 |pages= 338–348|bibcode= 2007EnvPr..26..338J }}</ref> Examples (aside from combustion of waste glycerol):
* [[Hydrogen]] [[gas]] production.<ref>{{cite journal |author1= Marshall, A. T. |author2 =Haverkamp, R. G. |title= Production of hydrogen by the electrochemical reforming of glycerol-water solutions in a PEM electrolysis cell |year= 2008 |journal= [[International Journal of Hydrogen Energy]] |volume= 33 |issue= 17 |pages= 4649–4654 |doi= 10.1016/j.ijhydene.2008.05.029|bibcode =2008IJHE...33.4649M }}</ref>
* [[Glycerine acetate]] is a potential fuel additive.<ref>{{cite journal |title= Acidic mesoporous silica for the acetylation of glycerol: Synthesis of bioadditives to petrol fuel |year= 2007 |journal= [[Energy & Fuels]] |volume= 21 |issue= 3 |pages= 1782–1791 |doi= 10.1021/ef060647q |last1= Melero |first1= Juan A. |last2= Van Grieken |first2= Rafael |last3= Morales |first3= Gabriel |last4= Paniagua |first4= Marta}}</ref>
* Additive for [[starch]] thermoplastic.<ref>{{Cite journal|last1=Özeren|first1=Hüsamettin D.|last2=Olsson|first2=Richard T.|last3=Nilsson|first3=Fritjof|last4=Hedenqvist|first4=Mikael S. |date=2020-02-01|title=Prediction of plasticization in a real biopolymer system (starch) using molecular dynamics simulations |journal=Materials & Design |language=en |volume=187|pages=108387|doi=10.1016/j.matdes.2019.108387|issn=0264-1275|doi-access=free}}</ref><ref>{{Cite journal|last1=Özeren|first1=Hüsamettin Deniz|last2=Guivier|first2=Manon|last3=Olsson|first3=Richard T.|last4=Nilsson|first4=Fritjof|last5=Hedenqvist|first5=Mikael S. |date=2020-04-07|title=Ranking Plasticizers for Polymers with Atomistic Simulations; PVT, Mechanical Properties and the Role of Hydrogen Bonding in Thermoplastic Starch |journal=ACS Applied Polymer Materials |volume=2|issue=5|pages=2016–2026|doi=10.1021/acsapm.0c00191|doi-access=free}}</ref>
* Conversion to various other chemicals:
** [[Propylene glycol]]<ref>{{cite press release |title= Dow achieves another major milestone in its quest for sustainable chemistries |date= 15 March 2007 |publisher= [[Dow Chemical Company]] |url= https://www.dow.com/propyleneglycol/news/20070315b.htm |access-date= 13 July 2007 |archive-url= https://web.archive.org/web/20090916061724/https://www.dow.com/propyleneglycol/news/20070315b.htm |archive-date= 16 September 2009 |url-status= dead }}</ref>
** [[Acrolein]]<ref>{{cite journal |doi= 10.1039/b506285c |title= The catalytic dehydration of glycerol in sub- and supercritical water: a new chemical process for acrolein production |journal= [[Green Chemistry (journal)|Green Chemistry]] |volume= 8 |issue= 2 |pages= 214–220 |year= 2006 |last1= Ott |first1= L. |last2= Bicker |first2= M. |last3= Vogel |first3= H.}}</ref><ref>{{cite journal |title= Acrolein synthesis from glycerol in hot-compressed water |journal= [[Bioresource Technology]] |year= 2007 |volume= 98 |pages= 1285–1290 |doi= 10.1016/j.biortech.2006.05.007 |pmid= 16797980 |issue= 6 |last1= Watanabe |first1= Masaru |last2= Iida |first2= Toru |last3= Aizawa |first3= Yuichi |last4= Aida |first4= Taku M. |last5= Inomata |first5= Hiroshi|bibcode= 2007BiTec..98.1285W }}</ref><ref>{{Cite journal |last1=Abdullah |first1=Anas |last2=Zuhairi Abdullah |first2=Ahmad |last3=Ahmed |first3=Mukhtar |last4=Khan |first4=Junaid |last5=Shahadat |first5=Mohammad |last6=Umar |first6=Khalid |last7=Alim |first7=Md Abdul |date=March 2022 |title=A review on recent developments and progress in sustainable acrolein production through catalytic dehydration of bio-renewable glycerol |url=https://linkinghub.elsevier.com/retrieve/pii/S0959652622005145 |journal=Journal of Cleaner Production |language=en |volume=341 |pages=130876 |doi=10.1016/j.jclepro.2022.130876|bibcode=2022JCPro.34130876A |s2cid=246853148 |url-access=subscription }}</ref>
** [[Ethanol]]<ref name="Yazdani">{{cite journal |author1= Yazdani, S. S. |author2 =Gonzalez, R. |title= Anaerobic fermentation of glycerol: a path to economic viability for the biofuels industry |year= 2007 |journal= [[Current Opinion in Biotechnology]] |volume= 18 |issue= 3 |pages= 213–219 |doi= 10.1016/j.copbio.2007.05.002 |pmid= 17532205}}</ref><ref>{{cite press release |date=27 June 2007 |title=Engineers Find Way To Make Ethanol, Valuable Chemicals From Waste Glycerin |website=ScienceDaily |url=https://www.sciencedaily.com/releases/2007/06/070626115246.htm}}</ref>
** [[Epichlorohydrin]],<ref>{{cite press release |publisher= [[Dow Chemical Company]] |url= https://epoxy.dow.com/epoxy/news/2007/20070326b.htm |title= Dow Epoxy advances glycerine-to-epichlorohydrin and liquid epoxy resins projects by choosing Shanghai site |date= 26 March 2007 |access-date= 21 February 2022 |archive-date= 8 December 2011 |archive-url= https://web.archive.org/web/20111208095306/http://epoxy.dow.com/epoxy/news/2007/20070326b.htm |url-status= live }}</ref> a raw material for [[epoxy resins]]

==Metabolism==
Glycerol is a precursor for synthesis of [[triacylglycerol]]s and of [[phospholipid]]s in the liver and [[adipose tissue]]. When the body uses stored fat as a source of energy, glycerol and [[fatty acid]]s are released into the bloodstream.

Glycerol is mainly metabolized in the liver. Glycerol injections can be used as a simple test for liver damage, as its rate of absorption by the liver is considered an accurate measure of liver health. Glycerol metabolism is reduced in both cirrhosis and [[fatty liver disease]].<ref>Glycerol clearance in alcoholic liver disease. Gut (British Society of Gastroenterology). 1982 Apr; 23(4): 257–264. D G Johnston, K G Alberti, R Wright, P G Blain</ref><ref>"Fatty liver disrupts glycerol metabolism in gluconeogenic and lipogenic pathways in humans". September 2018 ''The Journal of Lipid Research'', 59, 1685–1694. Jeffrey D. Browning, Eunsook S. Jin1, Rebecca E. Murphy, and Craig R. Malloy</ref>

Blood glycerol levels are highly elevated during [[diabetes]], and is believed to be the cause of reduced fertility in patients who suffer from diabetes and metabolic syndrome. Blood glycerol levels in diabetic patients average three times higher than healthy controls. Direct glycerol treatment of testes has been found to cause significant long-term reduction in sperm count. Further testing on this subject was abandoned due to the unexpected results, as this was not the goal of the experiment.<ref>''Molecular Human Reproduction'', Volume 23, Issue 11, November 2017, pp. 725–737</ref>

Circulating glycerol does not [[glycate]] proteins as do [[glucose]] or fructose, and does not lead to the formation of [[advanced glycation endproduct]]s (AGEs). In some organisms, the glycerol component can enter the [[glycolysis]] pathway directly and, thus, provide energy for cellular metabolism (or, potentially, be converted to glucose through [[gluconeogenesis]]).

Before glycerol can enter the pathway of glycolysis or gluconeogenesis (depending on physiological conditions), it must be converted to their intermediate [[glyceraldehyde 3-phosphate]] in the following steps:
<div class="toccolours" style="font-size:90%; margin:auto; display: flex; overflow-x: auto">
{{Biochem reaction subunit|compound=Glycerol|class=skin-invert-image|image=Glycerin Skelett.svg|image_size=100}}
{{Biochem reaction subunit|enzyme=Glycerol kinase|for_subst=ATP|for_prod=ADP}}
{{Biochem reaction subunit|compound=Glycerol-3-phosphate|class=skin-invert-image|image=Glycerol-3-phosphate.png|image_size=100}}
{{Biochem reaction subunit|enzyme=Glycerol-3-phosphate dehydrogenase|direction=reversible|for_subst=NAD<sup>+</sup>|for_prod=NADH|rev_prod=NAD<sup>+</sup>|rev_subst=NADH}}
{{Biochem reaction subunit|compound=Dihydroxyacetone phosphate|class=skin-invert-image|image=DHAP struct.svg|image_size=125}}
{{Biochem reaction subunit|enzyme=Triosephosphate isomerase|direction=reversible}}
{{Biochem reaction subunit|compound=Glyceraldehyde 3-phosphate|class=skin-invert-image|image=D-Glycerinaldehyde 3-phosphate Structural Formula V1.svg|image_size=150px}}
</div>
The enzyme [[glycerol kinase]] is present mainly in the liver and kidneys, but also in other body tissues, including muscle and brain.<ref>{{cite journal |pmc=1163884|pmid=183753|year=1976|last1=Tildon|first1=J. T.|title=Mitochondrial glycerol kinase activity in rat brain|journal=The Biochemical Journal|volume=157|issue=2|pages=513–516|last2=Stevenson|first2=J. H. Jr.|last3=Ozand|first3=P. T.|doi=10.1042/bj1570513}}</ref><ref>{{cite journal |title=Glycerol kinase activities in muscles from vertebrates and invertebrates|pmid=5801671 |pmc= 1187734 |volume=112|issue=4|date=May 1969|journal=Biochem. J.|pages=465–474|last1=Newsholme|first1=E. A.|last2=Taylor|first2=K|doi=10.1042/bj1120465}}</ref><ref>{{cite journal |vauthors= Jenkins, BT, Hajra, AK |date= 1976 |title= Glycerol Kinase and Dihydroxyacetone Kinase in Rat Brain |journal= Journal of Neurochemistry |volume= 26 |issue= 2 |pages= 377–385 |doi= 10.1111/j.1471-4159.1976.tb04491.x |pmid= 3631 |hdl= 2027.42/65297 |s2cid= 14965948 |url= https://deepblue.lib.umich.edu/bitstream/2027.42/65297/1/j.1471-4159.1976.tb04491.x.pdf |hdl-access= free |access-date= 27 August 2019 |archive-date= 21 February 2022 |archive-url= https://web.archive.org/web/20220221143240/https://deepblue.lib.umich.edu/bitstream/handle/2027.42/65297/j.1471-4159.1976.tb04491.x.pdf;jsessionid=27E5DB761F19C9F26C4F8EF4EDC33819?sequence=1 |url-status= live }}</ref> In adipose tissue, glycerol 3-phosphate is obtained from [[dihydroxyacetone phosphate]] with the enzyme [[glycerol-3-phosphate dehydrogenase]].

==Toxicity and safety==
Glycerol has very low toxicity when ingested; its [[LD50|LD<sub>50</sub>]] oral dose for rats is 12600&nbsp;mg/kg and 8700&nbsp;mg/kg for mice. It does not appear to cause toxicity when inhaled, although changes in cell maturity occurred in small sections of lung in animals under the highest dose measured. A sub-chronic 90-day nose-only inhalation study in [[Sprague Dawley]] rats exposed to 0.03, 0.16 and 0.66&nbsp;mg of glycerin per liter of air for 6-hour continuous sessions revealed no treatment-related toxicity other than minimal [[metaplasia]] of the [[epithelium]] lining at the base of the [[epiglottis]] in rats exposed to 0.66&nbsp;mg/L glycerin.<ref>{{cite journal | year = 2017 | title = Toxicity of the main electronic cigarette components, propylene glycol, glycerin, and nicotine, in Sprague–Dawley rats in a 90-day OECD inhalation study complemented by molecular endpoints | journal = Food and Chemical Toxicology | volume = 109 | issue = Pt 1| pages = 315–332 | doi = 10.1016/j.fct.2017.09.001  | last1 = Phillips | first1 = Blaine | last2 = Titz | first2 = Bjoern | last3 = Kogel | first3 = Ulrike | last4 = Sharma | first4 = Danilal | last5 = Leroy | first5 = Patrice | last6 = Xiang | first6 = Yang | last7 = Vuillaume | first7 = Grégory | last8 = Lebrun | first8 = Stefan | last9 = Sciuscio | first9 = Davide | last10 = Ho | first10 = Jenny | last11 = Nury | first11 = Catherine | last12 = Guedj | first12 = Emmanuel | last13 = Elamin | first13 = Ashraf | last14 = Esposito | first14 = Marco | last15 = Krishnan | first15 = Subash | last16 = Schlage | first16 = Walter K. | last17 = Veljkovic | first17 = Emilija | last18 = Ivanov | first18 = Nikolai V. | last19 = Martin | first19 = Florian | last20 = Peitsch | first20 = Manuel C. | last21 = Hoeng | first21 = Julia | last22 = Vanscheeuwijck | first22 = Patrick| pmid = 28882640 | doi-access = free }}</ref><ref>{{cite journal | last1 = Renne | first1 = R. A. | last2 = Wehner | first2 = A. P. | last3 = Greenspan | first3 = B. J. | last4 = Deford | first4 = H. S. | last5 = Ragan | first5 = H. A. | last6 = Westerberg | first6 = R. B. | year = 1992 | title = 2-Week and 13-Week Inhalation Studies of Aerosolized Glycerol in Rats | journal = International Forum for Respiratory Research | volume = 4 | issue = 2| pages = 95–111 | doi = 10.3109/08958379209145307| bibcode = 1992InhTx...4...95R }}</ref>
===Glycerol intoxication===
Excessive consumption by children can lead to glycerol intoxication.<ref>{{Cite web |last=Burrell |first=Chloe |date=2023-06-02 |title=Perth and Kinross parents warned as 'intoxicated' kids hospitalised by slushy drinks |url=https://www.thecourier.co.uk/fp/news/perth-kinross/4445065/perth-kinross-warning-slushy-drinks/ |access-date=2023-06-03 |website=The Courier |language=en-GB}}</ref> Symptoms of intoxication include [[hypoglycemia]], [[nausea]] and a [[Syncope (medicine)|loss of consciousness]]. While intoxication as a result of excessive glycerol consumption is rare and its symptoms generally mild, occasional reports of hospitalization have occurred.<ref>{{Cite web |title=Toddler 'turned grey and passed out' after drinking Slush Puppie |url=https://www.bbc.com/news/articles/c725pzqzdgno |access-date=2024-07-31|date=2024-07-31 |website=www.bbc.com |language=en-GB}}</ref> In the United Kingdom in August 2023, manufacturers of syrup used in [[slushy|slush ice drink]]s were advised to reduce the amount of glycerol in their formulations by the [[Food Standards Agency]] to reduce the risk of intoxication.<ref>{{Cite web |title='Not suitable for under-4s': New industry guidance issued on glycerol in slush-ice drinks |url=https://www.food.gov.uk/news-alerts/news/not-suitable-for-under-4s-new-industry-guidance-issued-on-glycerol-in-slush-ice-drinks |access-date=2023-08-11 |website=Food Standards Agency |language=en}}</ref> A 2025 study reported that between 2018 and 2024, at least 21 children aged 2–7 in the UK and Ireland received emergency treatment for symptoms of glycerol intoxication following the consumption of slush ice drinks.<ref name="times-intoxication">{{Cite news |last=Hayward |first=Eleanor |date=2025-03-12 |title=Slushie drinks have put at least 21 young children in hospital |url=https://www.thetimes.com/uk/healthcare/article/slushie-drinks-have-put-at-least-21-young-children-in-hospital-7hjn3snd0 |url-status=live |archive-url= https://archive.today/20250312002913/https://www.thetimes.com/uk/healthcare/article/slushie-drinks-have-put-at-least-21-young-children-in-hospital- |archive-date=2025-03-12 |access-date=2025-03-12 |work=[[The Times]] |language=en}}</ref><ref>{{Cite news |date=2025-03-12 |title=Doctors try to stop under-eights drinking slushies |url=https://www.bbc.co.uk/news/articles/c0l196l2k8ko |access-date=2025-03-12 |work=[[BBC News]] |language=en-GB}}</ref>

[[Food Standards Scotland]] advises that slush ice drinks containing glycerol should not be given to children under the age of 4, owing to the risk of intoxication. It also recommends that businesses do not use [[free refill]] offers for the drinks in venues where children under the age of 10 are likely to consume them, and that products should be appropriately labelled to inform consumers of the presence of glycerol.<ref>{{Cite web |title=Glycerol in slush ice drinks {{!}} Food Standards Scotland |url=https://www.foodstandards.gov.scot/consumers/food-safety/buying-food-eating-out/glycerol-in-slush-ice-drinks |access-date=2024-08-04 |website=www.foodstandards.gov.scot}}</ref>

==Historical cases of contamination with diethylene glycol==
On 4 May 2007, the FDA advised all U.S. makers of medicines to test all batches of glycerol for [[diethylene glycol]] contamination.<ref>{{cite web |publisher= U.S. Food and Drug Administration |url= https://www.fda.gov/bbs/topics/NEWS/2007/NEW01628.html |title= FDA Advises Manufacturers to Test Glycerin for Possible Contamination |date= 4 May 2007 |access-date= 8 May 2007 |archive-date= 7 May 2007 |archive-url= https://web.archive.org/web/20070507074219/http://www.fda.gov/bbs/topics/NEWS/2007/NEW01628.html |url-status= dead}}</ref> This followed an occurrence of [[Toxic cough syrup|hundreds of fatal poisonings in Panama]] resulting from a falsified import customs declaration by Panamanian import/export firm Aduanas Javier de Gracia Express, S. A. The cheaper diethylene glycol was relabeled as the more expensive glycerol.<ref>{{cite news |author= Walt Bogdanich |date= 6 May 2007 |url= https://www.nytimes.com/2007/05/06/world/06poison.html |title= From China to Panama, a Trail of Poisoned Medicine |work= The New York Times |access-date= 8 May 2007 |author-link= Walt Bogdanich |archive-date= 26 September 2015 |archive-url= https://web.archive.org/web/20150926084342/http://www.nytimes.com/2007/05/06/world/06poison.html |url-status= live }}</ref><ref>{{cite news |date= 20 February 2013 |url= https://www.topmastersinpublichealth.com/10-biggest-medical-scandals-in-history |title= 10 Biggest Medical Scandals in History |access-date= 21 February 2022 |archive-date= 8 January 2022 |archive-url= https://web.archive.org/web/20220108074814/https://www.topmastersinpublichealth.com/10-biggest-medical-scandals-in-history/ |url-status= usurped }}</ref> Between 1990 and 1998, incidents of DEG poisoning reportedly occurred in Argentina, Bangladesh, India, and Nigeria, and resulted in hundreds of deaths. In 1937, more than one hundred people died in the United States after ingesting DEG-contaminated [[elixir sulfanilamide]], a drug used to treat infections.<ref>{{Cite journal|last=Lang|first=Les|date=2007-07-01|title=FDA Issues Statement on Diethylene Glycol and Melamine Food Contamination|url=https://www.gastrojournal.org/article/S0016-5085(07)00995-X/abstract|journal=Gastroenterology|language=en|volume=133|issue=1|pages=5–6|doi=10.1053/j.gastro.2007.05.013|pmid=17631118|issn=0016-5085|access-date=25 December 2020|archive-date=21 February 2022|archive-url=https://web.archive.org/web/20220221143257/https://www.gastrojournal.org/article/S0016-5085%2807%2900995-X/fulltext|url-status=live|doi-access=free}}</ref>

==Etymology==
The origin of the ''gly-'' and ''glu''- prefixes for [[glycol]]s and sugars is from [[Ancient Greek]] {{lang|grc|γλυκύς}} ''glukus'' which means sweet.<ref>[https://www.dictionary.com/browse/glyco- glyco-] {{Webarchive|url=https://web.archive.org/web/20210430152747/https://www.dictionary.com/browse/glyco- |date=30 April 2021}}, dictionary.com</ref> Name ''glycérine'' was coined ca. 1811 by [[Michel Eugène Chevreul]] to denote what was previously called "sweet principle of fat" by its discoverer [[Carl Wilhelm Scheele]]. It was borrowed into English ca. 1838 and in the 20th c. displaced by 1872 term glycerol featuring an alcohols' suffix -ol.

==Properties==
Table of thermal and physical properties of saturated liquid glycerin:<ref>{{Cite book |last=Holman |first=Jack P. |title=Heat Transfer |publisher=McGraw-Hill Companies, Inc. |year=2002 |isbn=9780072406559 |edition=9th |location=New York, NY |pages=600–606 |language=English}}</ref><ref>{{Cite book |last=Incropera 1 Dewitt 2 Bergman 3 Lavigne 4 |first=Frank P. 1 David P. 2 Theodore L. 3 Adrienne S. 4 |title=Fundamentals of Heat and Mass Transfer |publisher=John Wiley and Sons, Inc. |year=2007 |isbn=9780471457282 |edition=6th |location=Hoboken, NJ |pages=941–950 |language=English}}</ref>
: {|class="wikitable mw-collapsible mw-collapsed"
!Temperature (°C)
![[Density]] (kg/m<sup>3</sup>)
![[Specific heat capacity|Specific heat]] (kJ/kg·K)
![[Kinematic viscosity]] (m<sup>2</sup>/s)
![[Thermal conductivity|Conductivity]] (W/m·K)
![[Thermal diffusivity]] (m<sup>2</sup>/s)
![[Prandtl number]]
![[Bulk modulus]] (K<sup>−1</sup>)
|-
|0
|1276.03
|2.261
|{{val|8.31e-3}}
|0.282
|{{val|9.83e-8}}
|84700
|{{val|4.7e-4}}
|-
|10
|1270.11
|2.319
|{{val|3.00e-3}}
|0.284
|{{val|9.65e-8}}
|31000
|{{val|4.7e-4}}
|-
|20
|1264.02
|2.386
|{{val|1.18e-3}}
|0.286
|{{val|9.47e-8}}
|12500
|{{val|4.8e-4}}
|-
|30
|1258.09
|2.445
|{{val|5.00e-4}}
|0.286
|{{val|9.29e-8}}
|5380
|{{val|4.8e-4}}
|-
|40
|1252.01
|2.512
|{{val|2.20e-4}}
|0.286
|{{val|9.14e-8}}
|2450
|{{val|4.9e-4}}
|-
|50
|1244.96
|2.583
|{{val|1.50e-4}}
|0.287
|{{val|8.93e-8}}
|1630
|{{val|5.0e-4}}
|}

==See also==
* [[Dioxalin]]
* [[Epichlorohydrin]]
* [[Nitroglycerin]]
* [[Oleochemical]]s
* [[Saponification]]/[[Soapmaking]]
* [[Solketal]]
* [[Transesterification]]

==References==
{{Reflist|30em}}

==External links==
* [https://gmd.mpimp-golm.mpg.de/Spectrums/06a47467-ce25-4606-9d46-01ca6d04585f.aspx Mass spectrum of glycerol] {{Webarchive|url=https://web.archive.org/web/20220213002237/http://gmd.mpimp-golm.mpg.de/Spectrums/06a47467-ce25-4606-9d46-01ca6d04585f.aspx |date=13 February 2022 }}
* [https://www.cdc.gov/niosh/npg/npgd0302.html CDC – NIOSH Pocket Guide to Chemical Hazards – Glycerin (mist)]

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