194 
ACIDS  OF  RHUBARB  STALKS,  TOMATOES,  ETC. 
ounces  of  juice;  the  dregs  were  washed  with  a  fresh  portion  of 
water  and  pressed  again  ;  the  resulting  liquors  were  then  mixed 
together  and  filtered,  and  evaporated  over  a  slow  water  bath  to 
the  consistence  of  a  thin  syrup,  and  set  aside  for  a  few  days,  for 
further  evaporation  and  to  crystallize ;  upon  examining  the 
crystals,  I  found  them,  to  be  very  irregular,  and  clotted  together  ; 
upon  recrystallizing  them  beautiful  white  crystals  were  obtained, 
resembling  in  appearance  "salt  of  sorrel,"  only  more  regular. 
The  crystals  were  of  a  rhomboidal  shape,  and  had  an  excessive- 
ly acid  taste.  They  agreed  in  form,  taste,  and  general  appear- 
ance with  other  samples  of  salt  of  sorrel. 
The  mother  liquor  then  from  the  first  crystallization  was  fur- 
ther evaporated,  and  set  aside  again  to  crystallize  ;  but  I  found 
that  although  still  strongly  acid,  it  would  not  crystallize,  owing, 
I  supposed,  to  its  excessive  thickness  or  tenacious  nature.  Be- 
ing aware  that  the  mother  liquor  of  tartaric  acid  and  of  crys- 
tallizable  sugar  acted  in  the  same  manner,  and  there  being 
nothing  else  as  yet  to  guide  me  in  assigning  a  reason  for  it,  I 
attributed  the  same  tendency  to  change  by  continued  heat 
to  the  acid  in  rhubarb. 
2.  Suspecting  this  acid  liquor  contained  potassa,  I  proceeded 
in  the  following  manner  to  ascertain  the  fact.  I  evaporated 
the  above  syrupy  mother  liquor  to  the  consistence  of  an  extract, 
then  placed  it  in  a  crucible  and  exposed  it  to  a  gentle  heat  for 
about  an  hour,  to  destroy  the  organic  matter  ;  the  incinerated 
remains  were  then  treated  with  hot  water  to  dissolve  out  the 
potassa ;  the  solution  was  then  evaporated  to  dryness,  when 
there  remained  evidently  a  portion  of  carbonate  of  potassa. 
This  dry  carbonate  weighed  nearly  two  and  a  quarter  grains, 
indicating  an  equivalent  of  four  and  three  quarter  grains  of 
binoxalate  of  potassa. 
3.  One  pound  of  fresh  stems  of  rhubarb  yielded  by  expres- 
sion thirteen  fluid  ounces  of  juice,  which  when  filtered  only 
measured  twelve  and  a  half  ounces,  leaving  about  half  an  ounce 
of  fibrous  matter  in  the  filter.  The  juice  was  then  evaporated, 
and  allowed  to  crystallize  ;  as  before  mentioned,  and  upon  a 
second  crystallization,  it  yielded  crystals  of  a  beautiful  color,  to 
the  amount  of  seventy  grains. 
