ACIDS  OF  RHUBARB  STALKS,  TOMATOES,  ETC. 
199 
our  gardens,  and  the  fruit  much  improved,  owing  to  the  great 
demand  there  is  for  it  in  making  tarts  and  jellies. 
But  the  examination  of  the  juice  was  at  first  tedious  and 
baffling,  owing  in  a  great  measure  to  the  large  amount  of  mucil- 
aginous matter  diffused  through  the  fruit.  The  great  difficulty 
to  contend  with  in  trying  to  crystallize  the  juice  alone  without 
combining  it  with  other  salts,  arose  from  the  mucilaginous  mat- 
ter [pectin,  &c]  which  on  cooling  had  a  tendency  to  gelatinize. 
But  with  repeated  experiments  I  am  happy  to  state  the  result 
is  more  than  I  anticipated. 
11.  I  extracted  the  juice  from  one  pound  of  Cydonia  Vulgaris, 
or  quince,  treating  it  in  the  same  way  as  the  tomato,  and  obtain- 
ed twelve  ounces  of  juice. 
The  acid  juice  was  then  precipitated  with  a  concentrated  so- 
lution of  acetate  of  lead,  and  the  precipitate  thoroughly  wash- 
ed with  cold  water. 
The  washed  precipitate  was  then  boiled  in  hot  water  a  few 
minutes,  and  allowed  to  stand  until  the  precipitate  subsided  ;  the 
clear  liquor  poured  off,  it  was  allowed  to  boil  again  ;  and  while 
it  was  suspended  in  the  hot  water,  was  decomposed  with  sul- 
phuretted hydrogen,  and  the  black  precipitate  washed  with  suc- 
cessive portions  of  hot  water.  The  filtered  liquor  was  then 
evaporated  over  a  slow  water  bath  to  four  ounces,  and  set  aside  ; 
on  cooling,  it  crystallized  in  beautiful  transparent  needle-shaped 
crystals.  The  mother  liquor  was  poured  off,  and  the  crystals 
thrown  on  bibulous  paper  and  allowed  to  dry  in  a  very  dry  at- 
mosphere. The  mother  liquor  was  further  evaporated,  and  set 
aside  to  crystallize.  The  amount  of  bimalate  of  lead  thus  ob- 
tained from  one  pound  of  quince  was  twenty  five  grains. 
The  crystals  are  of  a  beautiful  white  needle-shape,  and  deli- 
quescent. On  boiling  the  salt  in  hot  water  it  assumed  a  pitchy 
consistence,  which  on  cooling  is  rendered  very  brittle. 
In  the  above  mentioned  process,  the  potassa,  uniting  with  the 
acetic  acid  of  the  lead  salt,  was  washed  away  from  the  precipi- 
tate and  lost ;  but  by  evaporating  a  fresh  portion  of  juice  and 
burning  the  product,  I  found  that  one  pound  of  the  fruit 
yielded  ten  grains  of  dry  carbonate  of  potassa. 
It  will  be  perceived  from  the  foregoing  remarks  on  the  acid 
juices  above  named,  that  from  rhubarb  stems  was  obtained  bin- 
