Arachidic Acid
INCI Arachidic Acid. Saponified with NaOH it is listed as Sodium Arachidate. Also: Eicosanoic acid, Icosanoic acid, C20:0 fatty acid, Arachidic acid 98%.
Calculate a 100 % Arachidic Acid bar
That is stoichiometry on a measured composition rather than a guess, and it is about as well determined as a published figure: checked against the 35 Codex oils where both fields come from the same standard, the method's median error is 0.90 % and its 90th percentile 2.74 %, with no meaningful bias. The formula page shows the working. If you have a certificate of analysis for your lot, enter its measured value in the calculator and this estimate is set aside.
Published values
| Saponification value | not published |
| Derived from composition | 179.5 ± 3 % mg KOH/g |
| Used by the calculator | 179.5 mg KOH/g (derived) |
| SAP for NaOH | 0.1280 g/g |
| Iodine value | — |
| INS (SAP − IV) | — |
| Melting point | 73–79 °C |
| Unsaponifiable matter | — |
A bar made of 100 % Arachidic Acid
Conventional qualities summed from the fatty-acid groups; a single-oil bar is a reference point, not a recipe.
Fatty-acid profile
| Fatty acid | Published range, % | Used | |
|---|---|---|---|
| Arachidic acid | C20:0 · saturated | ≥ 97.5 | 97.5 |
Where these numbers come from
Specifications table on the product page: Appearance (Color) white or translucent; Form crystals, crystalline powder or flakes; Assay (GC) >= 97.5%; Melting Point (clear melt) 73-79 C (the page prints the degree sign as '?'). Header: CAS 506-30-9, C20H40O2, 312.54 g/mol. No acid, saponification or iodine value. The page was saved as HTML and converted to text (scripts removed, tags to line breaks, html.unescape). Catalogue number found through PubChem's vendor listing for CID 10467.
Specifications: Appearance (Color) white to almost white; Appearance (Form) crystalline powder or crystals or flakes; Infrared spectrum conforms; Melting point 72 C to 78 C; Titration with TBAH 97.5 to 102.5 %; GC >= 97.5 %. The GC line sits behind the page's 'View more' and was read from the specification list in the page's embedded schema.org data; the other lines are in the visible table as well.
Product information: purity >99%, storage room temperature, supplied neat, physical state solid; identifiers CAS 506-30-9, molecular weight 312.53, lipid number C20:0; synonyms include arachidic acid. No titration values, no melting point.
Checked and not used, to show that C20 is sold only as a minor acid in behenic and hydrogenated long-chain cuts. RADIACID 0161 ('Hydrogenated long chain fatty acid with typical C22 content'): C16 2 - 6, C18 31 - 42, C20 7 - 13, C22 42 - 54 %(m/m). RADIACID 0560 (https://www.oleon.com/products-solutions/radiacid-0560, 'BEHENIC ACID'): C20 <= 9, C22 86.0 - 89.0 %(m/m). Found by reading every RADIACID page listed in oleon.com/sitemap.xml.
Arachidic acid is eicosanoic acid, C20:0, the saturated fatty acid two carbons longer than stearic; arachis (peanut) oil gave it its name. Sold on its own it is a fine chemical: no oleochemical producer checked for this record sells an arachidic acid grade. Oleon's C20-bearing products are behenic acids or hydrogenated long-chain cuts in which C20 is the minor acid (RADIACID 0161, hydrogenated long chain fatty acid: C16 2-6 %, C18 31-42 %, C20 7-13 %, C22 42-54 %; RADIACID 0560, behenic acid: C20 <= 9 %, C22 86.0-89.0 %), and Koster Keunen lists behenic acid but no arachidic acid. So the record rests on laboratory producers' specifications, which give purity and a melting range but no titration value in mg KOH/g. What this record holds: Thermo Scientific Chemicals' Arachidic acid, 98% (catalogue A19616, formerly Alfa Aesar) specifies Assay (GC) >= 97.5 %, melting point (clear melt) 73-79 C, appearance white or translucent, form crystals, crystalline powder or flakes; CAS 506-30-9, C20H40O2, 312.54 g/mol. The assay is recorded as arachidic min 97.5 and the clear-melt range as the melting point. The same producer's Eicosanoic acid, 98% (catalogue 117720010, formerly Acros Organics) specifies GC >= 97.5 %, titration with TBAH 97.5 to 102.5 %, melting point 72-78 C, appearance white to almost white, infrared spectrum conforms. Larodan's research-grade eicosanoic acid (product 10-2000) is >99 % pure, molecular weight 312.53, lipid number C20:0, solid. The two catalogue assays and Larodan's purity agree, and nothing else in any of these products is itemised, so the profile holds arachidic alone. sapKohMgPerG is null because no producer publishes a saponification value. The TBAH titration is an assay of carboxylic acid content, expressed as a percentage of pure eicosanoic acid; it is neither an acid value in mg KOH/g nor a saponification value, so it is not filed as either. On the arithmetic, which is arithmetic and not a measurement: a free fatty acid takes one KOH per molecule, so pure C20:0 (M 312.53) is 56106 / 312.53 = 179.5 mg KOH/g, between stearic acid's 56106 / 284.48 = 197.2 and behenic acid's 56106 / 340.58 = 164.7; the build derives the same figure from the recorded profile and labels it derived. iodineValue is null: nobody publishes one, though a fully saturated acid must be near zero. unsaponifiablePercent is null: not published. No source consulted prints an INCI name; the INCI name, CAS and EC numbers are CosIng's entry for Arachidic Acid, which also lists Sodium Arachidate (there is no potassium salt entry). In soap, arachidic acid behaves like a harder, slower-dissolving stearic acid: it raises the melting point and hardness of the bar, and like behenic acid it is better used at a few percent than as a major fat.
This record is part of the open ingredient database (ODbL). Found an error or a better primary source? The dataset is on GitHub; corrections with a document link are welcome.