552       DIFFERENCES  OF  ACTION  BETWEEN  POTASSA  AND  SODA. 
of  potassa  in  certain  proportions,  it  is  capable,  on  the  contrary,  of 
aiding  in  an  abundant  production  of  this  acid. 
I  will  begin  by  indicating  the  quantities  of  oxalic  acid  which  I 
have  obtained  by  treating  various  organic  matters  with  hydrate  of 
potassa,  remarking  that  several  belonging  to  the  ligneous  genus, 
might  be  considered  as  having  among  themselves  a  great  analogy 
of  elementary  composition,  producing,  nevertheless,  very  various 
quantities  of  oxalic  acid. 
After  having  tried  a  great  number  of  different  estimations,  I 
stopped  at  the  following,  as  being  equally  well  adapted  to  the  com- 
parative treatment  of  several  different  matters. 
The  following  are  the  principal  results:  — 
Hydrate  of  Potassa.           Dried  at  100° 
Product=Oystallized 
C. (212° 
F.) 
oxalic  acid. 
300+100  Fecula  dried. 
Mean  of  10  operations 
=  125 
300+100  Sawdust  of  various 
woods. 
)> 
20 
33 
=  70 
300+100  Straw  of  cereals  . 
10 
33 
=100 
300+100  Hay  from  various 
sources 
?> 
20 
j> 
=140 
300+100  Trefoil 
33 
4 
33 
=  110 
300+100  Lucerne 
33 
4 
)> 
=110 
300+100  Tansy 
33 
4 
33 
=130 
300+100  Mugwort  . 
33 
2 
;> 
=  115 
300+100  Wild  chicory 
33 
2 
33 
=120 
300  +  100  Borage 
3) 
2 
33 
=  112 
300+100  Nettles 
33 
2 
3> 
=100 
300+100  Tobacco  stalks  . 
33 
4 
33 
=150 
300+100  Bran  of  cereals  . 
33 
4 
j> 
=150 
300+100  Pure  woollen  rags 
33 
4 
35 
=  10 
300+100  Pure  silk  rags 
*3 
2 
33 
=  12 
300+100  Leather 
33 
2 
33 
=  6 
300+100  Horn  . 
33 
2 
33 
=  20 
These  experiments  were  conducted  in  the  following  manner: — 
1   For  fecula  the  caustic  liq.  was  first  concentrated  until  its 
boiling  point  reached  225°  C.  (437°  F.)  then  cooled  to  180°  C. 
(356°  F.);  then  the  fecula  was  added  by  small  portions  at  a  time, 
the  temperature  being  maintained  between  200°  and  225°  C.  (392° 
