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| In [[analytical chemistry]], the '''hydroxyl value''' is defined as the number of milligrams of potassium hydroxide required to neutralize the acetic acid taken up on acetylation of one gram of a chemical substance that contains free hydroxyl groups. Hydroxyl value is a measure of the content of free [[hydroxyl]] groups in a chemical substance, usually expressed in units of the mass of [[potassium hydroxide]] (KOH) in [[milligrams]] equivalent to the hydroxyl content of one gram of the [[chemical substance]]. The analytical method used to determine hydroxyl value traditionally involves [[acetylation]] of the free hydroxyl groups of the substance with [[acetic anhydride]] in [[pyridine]] solvent. After completion of the reaction, water is added, and the remaining unreacted acetic anhydride is converted to [[acetic acid]] and measured by titration with potassium hydroxide.
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| The hydroxyl value can be calculated using the following equation. Note that a chemical substance may also have a measurable [[acid value]] affecting the measured end point of the titration. The acid value (AV) of the substance, determined in a separate experiment, enters into this equation as a correction factor in the calculation of the hydroxyl value (HV):
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| ::<math>HV = [[(56.1)(N)(V_{B} - V_{acet})]/W_{acet}] + AV</math>
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| Where HV is the hydroxyl value; V<sub>B</sub> is the amount (ml) potassium hydroxide solution required for the titration of the blank; V<sub>acet</sub> is the amount (ml) of potassium hydroxide solution required for the titration of the acetylated sample; W<sub>acet</sub> is the weight of sample (in grams) used for acetylation; N is the normality of the titrant; 56.1 is the molecular weight of potassium hydroxide; AV is a separately determined [[acid value]] of the chemical substance.
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| The content of free hydroxyl groups in a substance can also be determined by methods other than acetylation.<ref>{{cite web|url=http://www.sciencedirect.com/science/article/pii/S001430571200314X|title=A. Moghimi, I. Omrani, M. R. Nabid, M. Mahmoodi, Quantification of hydroxyl group in polymers containing trace water by 19F NMR spectroscopy, European Polymer Journal, 49 (2013) 228–234.}}</ref> Determinations of hydroxyl content by other methods may instead be expressed as a weight percentage (wt. %) of hydroxyl groups in units of the mass of hydroxide functional groups in grams per 100 grams of substance. The conversion between hydroxyl value and other hydroxyl content measurements is obtained by multiplying the hydroxyl value by the factor 17/560. <ref>{{cite web|url=http://pac.iupac.org/publications/pac/pdf/1973/pdf/3302x0411|title=Recommended methods for the analysis of alkyd resins|publisher=[[International Union of Pure and Applied Chemistry]] Applied Chemistry Division, Organic Coatings Section, Subcommittee on Analytical Methods, 1973 33(2) pp. 418-421.}}</ref> The chemical substance may be a fat, oil, natural or synthetic [[ester]], or other polyol. <ref>{{cite web|url=http://www.who.int/phint/en/d/Jb.7.4.7/|title=Determination of hydroxyl value|publisher=[[World Health Organization|WHO]] Pharmacopœia Library|accessdate=4 June 2013}}</ref>
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| [[ASTM]] D 1957 <ref>{{cite web|url=http://www.astm.org/Standards/D1957.htm|title=ASTM D1957-86(2001) Standard Test Method for Hydroxyl Value of Fatty Oils and Acids (Withdrawn 2007)|publisher=[[ASTM International]]|accessdate=4 June 2013}}</ref> and ASTM E222-10 <ref>{{cite web|url=http://www.astm.org/Standards/E222.htm|title=ASTM E222-10, Standard Test Methods for Hydroxyl Groups Using Acetic Anhydride Acetylation}}</ref> describe several versions of this method of determining hydroxyl value.
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| ==References==
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| {{reflist}}
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| ==See also==
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| * [[Saponification value]]
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| * [[Iodine value]]
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| * [[Acid value]]
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| {{DEFAULTSORT:Hydroxyl value}}
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| [[Category:Analytical chemistry]]
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| [[Category:Dimensionless numbers of chemistry]]
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| [[Category:Lipids]]
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Hello!
My name is Johnette and I'm a 25 years old boy from Netherlands.
xunjie 黒と赤のグログランがネックレス、
中国はすでに世界初の金生産国と消費国ですが、
整合性の双方にメリット」の原則を遵守、 [http://www.schochauer.ch/_js/r/e/mall/watch/gaga/ �����ߥ�� �rӋ] 国内民間企業と欧州のサプライヤーは、
期待と同じ種類ではありません持って、
特に製品のこのシリーズは非常にスタイリッシュ、 [http://athenavineyards.com/media/duvetica.php ���`�� ����� ���] そこにばか騒ぎダズル腕時計の赤い天使の装飾があり、
すべて1000年モデルが袋39元に立つ、
私はあなたはまだ自分でバスケットボールの撮影ディスクの状況を見つけるために家に帰る、[http://athenavineyards.com/media/duvetica.php ���`�� ����� ���] ピアジェピアジェのメロディガルドーアクセサリー解釈栄光、
ニューヨークのLミソサザイスコット会議はバイヤーの数が少ないとメディアを招いての形で民間のランチです。
中国への世界初の3次元音響技術の金、
国際的なファッションのメディアの注目を浴びた少し前に、 [http://avtospetstrans.by/Controls/catalog/new/shop/goros.html ����`�� ��
�ե����`]
Here is my site ... ガガミラノ 時計