484  Chemistry  of  Ipecacuanha.  {^l°Z\m^ 
would  be  increased  to  1,  and  its  sp.  volume  reduced  to  1 ;  and  if 
from  the  same  body  we  would  take  one-half  of  the  molecules  and 
leave  the  remaining  half  to  fill  the  same  space  as  was  occupied  by 
the  original  body,  then  its  sp.  gr.  would  be  reduced  to  -25  and  its 
sp.  volume  increased  to  4.  So  we  see  that  specific  gravity  is  purely 
a  mutable  signification,  entirely  dependent  upon  the  intrinsic  value 
of  matter  compared  to  a  standard  of  weight,  and  upon  density  which 
is  regulated  by  molecular  affinity,  gravity,  atmospheric  pressure 
and  heat. 
It  is  clear  that  a  proportion  of  the  atomic  weights  of  two  different 
bodies  could  not  be  in  ratio  with  the  sp.  gravities  of  these  bodies, 
because  atoms  of  different  elements  unite  in  different  numbers  to 
form  molecules,  and  the  atomic  weights  of  different  elements  are 
taken  at  different  temperatures,  while  sp.  gr.  is  always  taken  at  the 
same  temperature. 
The  impossibility  of  the  molecular  proportion  is  due  to  the  fact 
that  molecular  weight  is  a  constant  quantity,  being  derived  with  all 
the  elements  from  the  same  basis  and  under  similar  conditions,  while 
specific  gravity  is  a  variable  quantity,  being  derived  with  all  the 
elements  under  different  conditions,  upon  the  same  basis,  and,  as  the 
same  thing  differently  treated,  does  not  yield  the  same  result,  so  the 
specific  gravity  and  molecular  or  atomic  weight  of  the  same  sub- 
stance, differently  derived,  cannot  be  expected  to  be  proportionate 
in  any  way. 
THE  CHEMISTRY  OF  IPECACUANHA.1 
Dr.  B.  H.  Paul  and  A.  J.  Cownley. 
Next  to  opium  and  cinchona  bark,  ipecacuanha  is  probably  one  of 
the  most  important  drugs  included  in  the  official  materia  medica,  but 
its  chemical  history  is  still  very  imperfect,  and  although  some  of  its 
medicinal  effects  are  ascribed  to  an  alkaloid,  there  is  considerable 
doubt  whether  that  is  always  the  case. 
For  several  months  past  we  have  been  engaged  in  the  endeavor 
to  devise  a  satisfactory  method  of  extracting  from  ipecacuanha  the 
alkaloid  which  has  been  regarded  as  the  active  principle  of  this 
drug,  and  to  which  the  name  of  emetine  has  been  applied ;  our 
object  being  to  obtain  such  means  of  quantitative  determination  as 
1  From  Pharm.  Jour.  Trans.,  July  22,  1893,  p.  61. 
