D-(-)-l-tartaric acid, the unnatural or unusual stereoisomer.
Post 506241 (https://www.thevespiary.org/talk/index.php?topic=13322.msg50624100#msg50624100)
(Rhodium: "chirality of otc tartrate salts", Tryptamine Chemistry)
Post 511856 (https://www.thevespiary.org/talk/index.php?topic=7748.msg51185600#msg51185600)
(Rhodium: "the freebase should be used", Stimulants)
Or you could've consulted TiHKAL about it...
(or, as an encouraged researcher, you could verify it this way: crystallize the salt using one stereoisomer of tartaric acid, and crystallize everything left with maleic acid... - then TASTE some... you should be able to distinguish rather sharply between d- and l-LSD... ;) )
indole_amine