MOLECULAR  DISSYMMETRY  OF  ORGANIC  PRODUCTS. 
Physical  aspect,  lustre  of  the  crystals,  solubility,  specific  grav- 
ity, single  or  double  refraction,  all  is  not  only  alike,  similar, 
very  near,  but  identical  in  the  most  rigorous  acceptation  of 
the  word. 
This  identity  is  the  more  remarkable  as  we  shall  see  it  re- 
placed by  a  general  and  considerable  opposition  of  the  proper- 
ties of  these  same  substances,  when  they  are  found  in  particular 
conditions  which  I  am  about  to  point  out. 
We  have  seen  that  we  must  distribute  all  chemical  compounds, 
artificial  or  natural,  mineral  or  organic,  in  two  great  classes; 
compounds  non-dissymmetric  with  superposable  image,  and  com- 
pounds dissymmetric  with  non-superposable  image. 
This  stated,  the  identity  of  properties,  of  which  I  have  just 
spoken  in  the  two  tartaric  acids  and  their  similar  derivatives, 
constantly  exists  with  the  absolute  characters  I  have  named, 
whenever  these  substances  are  placed  in  presence  of  any  com- 
pound of  the  class  of  bodies  with  superposable  image,  such  as  po- 
tassa,  soda,  ammonia,  lime,  barytes,  aniline,  alcohol,  the  ethers — 
in  a  word,  of  all  compounds,  whatever  they  may  be,  not  dissym- 
metric, not  hemihedric  in  form,  without  action  on  polarized  light. 
Submit  them,  on  the  contrary,  to  products  of  the  second  class 
with  non-superposable  image,  asparagine,  quinine,  strychnine, 
brucine,  albumen,  sugar,  &c,  &c,  bodies  dissymmetric  like 
them,  all  changes  in  an  instant.  Solubility  is  no  longer  the 
same.  If  there  is  combination,  the  crystalline  form,  specific 
gravity,  the  quantity  of  water  of  crystallization,  the  more  or 
less  ready  destruction  by  heat,  all  differ  as  much  as  the  most 
distant  isomeric  bodies  differ. 
Here  then  we  have  the  molecular  dissymmetry  of  bodies  in- 
troducing itself  in  chemistry  as  a  powerful  modifier  of  chemical 
affinities.  In  presence  of  the  two  tartaric  acids,  quinia  does  not 
behave  like  potassa  only  because  it  is  dissymmetric,  and  potassa 
is  not.  Molecular  dissymmetry  is  hence  offered  as  a  property 
capable  by  itself,  as  far  as  dissymmetry,  of  modifying  chemical 
affinities.  I  do  not  believe  any  discovery  has  yet  entered  so  far 
into  the  mechanical  part  of  the  problem  of  combinations. 
Let  us  endeavor  to  present  the  cause  of  these  identities  and 
of  these  dissemblances.  Let  us  suppose  a  dextrorse  helix  and  a 
sinistrorse  helix  separately  penetrating  two  blocks  of  identi- 
