app ears ▁on ▁cool ing , ▁and ▁is ▁changed ▁to ▁blue ▁or ▁vio let ▁by ▁al de hy des . ▁ ▁En anti om ers ▁Natur ally - occ urr ing ▁con i ine ▁is ▁present ▁in ▁Con ium ▁mac ul atum ▁as ▁a ▁mixture ▁of ▁the ▁R -( − )- ▁and ▁S -( + )- en anti om ers . ▁The ▁s tere och em ical ▁composition ▁of ▁" con i ine " ▁is ▁a ▁matter ▁of ▁some ▁importance , ▁since ▁its ▁two ▁en anti om ers ▁do ▁not ▁have ▁identical ▁bi ological ▁properties , ▁and ▁many ▁of ▁the ▁older ▁ph arm ac ological ▁studies ▁on ▁this ▁comp ound ▁were ▁carried ▁out ▁using ▁the ▁naturally - occ urr ing ▁is omer ic ▁mixture . ▁ ▁The ▁common ▁criter ion ▁for ▁en anti omer ic ▁hom ogene ity ▁is ▁the ▁specific ▁rotation , ▁[ α ] D , ▁a ▁value ▁that ▁depends ▁on ▁such ▁factors ▁as ▁temperature , ▁sol vent ▁and ▁concentration ▁of ▁the ▁analy te . ▁Modern ▁values ▁for ▁the ▁specific ▁rotation ▁of ▁the ▁en anti om ers ▁of ▁con i ine ▁are ▁as ▁follows : ▁▁ ▁S -( + )- Con i ine , ▁identical ▁to ▁D -( + )- con i ine , ▁has ▁[ α ] D ▁= ▁+ 8 . 4 ° ▁( c ▁= ▁ 4 . 0 , ▁in ▁CH Cl 3 ). ▁These ▁authors ▁note ▁that ▁L aden burg ' s ▁value , ▁+ 1 5 ° , ▁is ▁for ▁a ▁" ne at "