A^PteXvPmT'}     Rhlls  Glabra  and  Rhus  Typhina.  405 
Chemical  Constituents. 
In  the  course  of  this  investigation  the  question  naturally  arose 
as  to  the  relative  value  of  the  several  species  of  Rhus  with  hairy 
fruits  containing  a  crimson,  acid  cell  sap.  A  number  of  acids  have 
been  identified  and  these  include  malic  acid,  citric  acid,  gallic  acid, 
and  tannic  acid.  Some  of  these  are  free  and  may  also  be  combined 
with  calcium  and  possibly  other  inorganic  bases.  In  order  to  get 
an  idea  of  the  relative  amounts  of  free  acid  in  these  two  species 
under  consideration,  infusions  were  made  and  these  were  titrated 
with  a  volumetric  solution  of  sodium  hydroxide.  The  method  that 
was  employed  was  the  following:  10  Gm.  of  the  commercial  fruits, 
air  dried,  were  ground  in  a  wedgewood  mortar  and  placed  in  a 
beaker  with  100  c.c.  of  distilled  water.  The  mixture  was  heated 
for  from  15  to  20  minutes  on  a  water  bath  and  filtered  through 
filter  paper,  the  portion  remaining  on  the  filter  being  washed  until 
the  filtrate  measured  200  c.c.  This  was  then  divided  into  two  por- 
tions and  titrated  with  a  sodium  hydroxide  solution,  each  c.c.  of 
which  contained  0.004749  grams  of  sodium  hydroxide.  The  infu- 
sions of  these  fruits  yield  solutions  which  are  of  a  deep  wine  color 
and  acid  to  litmus.  Upon  the  addition  of  the  alkali  the  color  is  first 
darkened,  then  changes  to  an  olive-green,  especially  when  viewed 
in  thin  layers.  If  at  this  point  phenolphthalein  is  added  and  the 
titration  carried  further  it  will  be  found  that  nearly  an  equal 
volume  of  sodium  hydroxide  solution  is  necessary  to  neutralize 
it  as  indicated  by  the  formation  of  a  red  color  of  the  solution 
due  to  the  phenolphthalein.  It  should  be  stated  that  this  end 
reaction  can  only  be  accurately  determined  when  the  solution  is 
viewed  in  thin  layers.  The  technic  in  titration  consists  essentially 
in  adding  the  alkali,  drop  by  drop  from  a  burette,  to  the  original 
infusion  of  the  berries  until  the  color  becomes  an  olive  green,  the 
phenolphthalein  is  then  added  and  the  titration  continued  until  a 
slight  reddish  tint  is  observed.  Specimens  which  were  employed 
were  fruits  which  had  been  gathered  several  years  ago  and  it  is 
likely  that  fresh  fruits  will  show  a  higher  per  cent,  of  acidity. 
The  fruits  of  Rhus  glabra  have  been  of  interest  to  investigators 
for  a  great  many  years  and  there  are  a  number  of  papers  of  interest 
in  this  connection.  The  first  chemical  work  on  the  nature  of  the 
acid  sap  of  the  fruits  of  Rhus  glabra  is  that  of  I.  Cozzens  8  in  the 
Annals  of  the  Lyceum  of  New  York  who  reported  that  it  contained 
