354 
ON  THE  RESIN  OF  JALAP. 
The  resin,  melted  at  302°  F.,  lost  1  equiv.  of  water,  and  gave — 
Carbon      -       -       54*86     55-21     72  55*38 
Hydrogen       -       -     8*04      8*00     60  7-69 
Oxygen       -       -       37*10     36*79     36  36*93 
Mayer  states  that  he  would  not  have  ventured  to  assign  to  this 
body  so  high  an  atomic  weight  except  on  account  of  the  combina- 
tions of  the  modification  soluble  in  water  and  its  products  of  decom- 
position. 
Rhodeoretine  is  but  slightly  soluble  in  water,  very  soluble  in 
alcohol,  insoluble  in  ether.  The  alcoholic  solution  is  precipitated 
both  by  water  and  alcohol.  It  is  soluble  in  potash,  soda,  ammonia 
and  baryta  water,  more  quickly  when  warm.  Acids  do  not  again 
precipitate  it  from  these  solutions ;  it  has  become  soluble  in  water. 
It  is  little  soluble  in  cold  solutions  of  carbonate  of  soda  or  potash, 
more  so  when  boiled.  It  dissolves  readily  in  acetic  acid,  very 
slowly  in  cold  dilute  nitric  acid,  more  quickly  and  with  decom- 
position when  heat  is  applied  ;  concentrated  nitric  acid  acts  upon 
it  energetically,  with  considerable  evolution  of  nitrous  oxide  and 
elevation  of  temperature.  Concentrated  sulphuric  acid  dissolves 
the  resin,  and  communicates  a  beautiful  red  color,  which  changes 
to  brown  in  a  few  hours.  If  the  solution  is  diluted  with  water 
while  red,  a  brownish  oleaginous  body,  of  agreeable  odor,  resembling 
fresh  plums,  separates,  and  the  liquid  contains  sugar.  Heated  on 
platinum  foil,  the  resin  melts,  turns  brown,  and  burns  with  a  bright 
smoky  flame,  disengaging  a  peculiar  empyreumatic  odor,  resembling 
caramel.    A  coal  remains. 
Rhodeoretinic  Acid. — This  is  the  body  formed  by  the  action  of 
strong  bases  upon  the  above  resin.  The  change  consists  in  the 
assimilation  of  3  equivs.  of  water.  It  was  prepared  by  introducing 
100  grms.  of  pure  rhodeoretine  into  1  lb.  of  baryta-water,  and  stir- 
ring the  mixture  while  heating  till  it  boiled.  The  resin  dissolved 
quickly  and  entirely.  The  baryta  was  separated  from  the  cold 
solution  by  sulphuric  acid  in  very  slight  excess,  which  was  re- 
moved by  means  of  carbonate  of  lead.  The  colorless  filtrate, 
evaporated  to  dryness  in  a  water-bath,  left  a  substance  exactly  re- 
sembling rhodeoretine,  except  that  it  is  very  hygroscopic.  Above 
212°  F.  it  softens,  and  melts  between  212°  and  248°  F.  Above 
248°  F.  decomposition  commences.  It  has  no  smell ;  the  aqueous 
solution  has  a  smell  very  much  like  quinces  and  a  strong  acid  re- 
