粘酸（Mucic acid），又称
半乳糖二酸（Galactaric acid），化学式为C6H10O8，分子量210.139，CAS登录号526-99-8。其密度为1.9±0.1 g/cm3，熔点220-225℃（分解），沸点766.4±60.0℃，闪点431.2±29.4℃，常温下蒸汽压为0mmHg，外观为白色至灰白色结晶粉末。
Galactaric acid~Tetrahydroxyadipic acid; Galactaric acid; hexaric acid; D-galactaric acid; (2R,3S,4R,5S)-2,3,4,5-tetrahydroxyhexanedioate (non-preferred name); (2S,3R,4R,5S)-2,3,4,5-tetrahydroxyhexanedioate (non-preferred name); (2S,3R,4S,5S)-2,3,4,5-tetrahydroxyhexanedioate (non-preferred name); 2,2,3,3-tetrahydroxyhexanedioic acid