196         ACIDS  OF  KHUBARB  STALKS,  TOMATOES,  ETC. 
mass  was  then  treated  with  hot  water,  filtered,  evaporated 
to  dryness,  and  when  carefully  collected,  weighed  four  and  a 
quarter  grains. 
Seeing  that  the  amount/  of  potassa  did  not  agree  with  that  of 
the  binoxalate  according  to  the  tables  in  the  U.  S.  Dispensatory, 
and  repeating  the  test  over  and  over  again,  I  then  attribu- 
ted the  difference  to  some  impurities  existing  in  the  crystals, 
which  I  had  not  got  rid  of  before  the  process  of  crystallization ; 
but  on  examining  the  above  processes,  I  found  them  correctly 
made,  and  therefore  believed  that  something  was  wrong  in  the 
calculation. 
On  examining  the  U.  S.  Dispensatory,  I  found  it  to  state  the 
atomic  weight  of  binoxalate  of  potassa,  without  allowing  for  the 
water  of  crystallization  making  it,  119-2,  which  had  led  me  into 
the  above  error  of  calculation.  On  heating  a  few  grains  of  the 
crystals,  ebullition  ensued,  showing  the  existence  of  water  of 
crystallization  ;  which  also  showed,  that  there  must  be  an  omis- 
sion in  the  quotation  of  the  Dispensatory. 
Being  greatly  surprised  at  the  result,  and  suspecting  some 
fallacy  existing  somewhere,  I  examined  the  Dispensatory  again, 
along  with  Turner's  Chemistry,  and  found  that  Turner  quoted 
binoxalate  of  potassa  as  containing  three  atoms  of  water,  mak- 
ing 146.  instead  of  119.  Now  resuming  my  calculations  I 
found  that  the  acid  salt  in  rhubarb  agreed  in  the  amount  of  po- 
tassa to  the  binoxalate  as  stated  above. 
The  Tomato, 
I  then  proceeded  to  investigate  the  tomato  (Solanum  Lyco- 
persicum),  red  variety,  which  from  its  very  extensive  and  popu- 
lar use  needs  no  further  comment  than  merely  stating  the  origi- 
nal source  of  the  vegetable,  which  was  from  South  America, 
where  it  was  very  much  esteemed  amongst  the  Portuguese  and 
Spaniards  for  making  a  sauce,  considered  by  them  very  nutri- 
tive and  cooling ;  probably  owing  to  the  acidulous  properties 
contained  in  it. 
According  to  my  experiments,  the  acid  seems  to  exist  as  an 
acid  salt,  but  the  quantity  of  acid  obtained  in  a  crystalline  form 
from  one  pound  is  a  very  small  amount. 
8.  One  pound  of  freshly  selected  fruit  of  the  Solanum  Lyco- 
