MOLECULAR  DISSYMMETRY  OF  ORGANIC  PRODUCTS.  107 
VIII. 
Only  because  chemistry  has  been  up  to  the  present  time  power- 
less in  the  preparation  of  dissymmetric  bodies,  might  we  fear 
that  we  may  be  always  ignorant  of  the  mode  of  production  of 
the  inverse  bodies  of  natural  organic  substances.  Happily  this 
fear  is  exaggerated.  I  have  ascertained  indeed  that,  by  ordi- 
nary chemical  processes,  such  as  the  action  of  heat,  a  right  body 
can  be  changed  to  its  left,  and  inversely.  Thus  in  warming 
right  tartaric  acid  under  certain  determinate  conditions,  which 
it  would  be  too  long  to  specify  here,  it  is  transformed  into  left 
tartaric  acid,  or  rather  into  paratartaric  acid  ;  and  inversely, 
under  the  same  conditions  exactly,  left  tartaric  acid  becomes 
right. 
Here  are  ten  or  twelve  grammes*  of  entirely  pure,  left  tar- 
taric acid,  which  were  thus  procured.  Their  preparation  cost 
me  much  trouble.  But  M.  Biot  desired  to  study  in  a  very  par- 
ticular manner  the  characters  of  dispersion  of  this  left  tartaric 
acid,  so  remarkable  on  account  of  its  origin.  He  desired  him- 
self to  be  at  the  cost  of  the  operation ;  very  expensive,  because 
the  transformation  depends  upon  the  employment  of  the  tartrate 
of  cinchonine  or  of  quinine,  and  the  base  is  lost  because  the  tar- 
trate must  be  heated  to  a  temperature  which  destroys  it. 
I  have  prepared  by  this  process  sufficient  paratartaric  acid  to 
take  from  it  twelve  grammes  of  left  tartaric  acid,  which  presents 
rigorously,  in  an  inverse  sense,  the  same  optical  characters  as 
tartaric  acid. 
Every  analogous  transformation  of  a  natural  dissymmetric 
body  into  its  inverse,  should  be  regarded  as  a  great  advance  in 
organic  chemistry. 
IX. 
At  the  conclusion  of  our  first  lecture,  I  alluded  to  observations 
to  which  it  is  time  we  should  give  all  the  attention  they  merit. 
These  observations  are  relative  to  the  comparison  of  the  physical 
and  chemical  properties  of  right  and  corresponding  left  isomerics. 
I  have  already  insisted  upon  the  perfect  identity  of  all  their  pro- 
perties, excepting,  however,  the  inversion  of  their  crystalline 
forms,  and  the  opposition  of  direction  of  their  optical  deviations. 
*  A  gramme  is  equal  to  about  15|  grs. — Tr. 
