462  Assay  of  Gum  Arabic  and  G.  Senegal.  {*m-g™£-Jfj£rm- 
(7)  Mixtures  of  the  two  gums  behave  towards  potash  and  copper 
sulphate  like  pure  gum  Senegal,  but  on  boiling  with  potash  alone 
the  mixture  turns  amber-yellow. 
(8)  Mixtures  of  gum  arabic  and  dextrin  behave  towards  potash 
and  copper  sulphate  like  pure  gum,  but  on  long  boiling  reduction 
takes  place  if  at  least  the  amount  of  dextrin  is  not  too  small. 
(9)  To  detect  small  quantities  of  dextrin  the  liquid  must,  after  a 
slight  warming,  be  filtered  before  boiling. 
(10)  In  similar  manner  the  separation  must  be  performed  when 
both  kinds  of  gum  are  present,  as  well  as  dextrin.  The  cupric 
precipitate  containing  both  gums  is  washed  with  distilled  water, 
dissolved  in  a  little  dilute  hydrochloric  acid,  and  mixed  with  a  large 
excess  of  spirit.    After  standing  for  a  day,  the  transparent  deposit 
,  is  dried,  then  dissolved  in  hot  water,  and  tested  according  to  4  and  6. 
The  assay  of  gum  arabic  may  also  be  prepared  according  to  the 
following  scheme  : 
(A)  The  appearance  of  the  sample  when  not  in  powder.  (See  1 
and  2.) 
(Z?)  Try  the  solubility  of  the  powdered  sample  in  warm  water. 
(See  3.)  If  the  sample  is  but  partially  soluble,  and  leaves  a  jelly- 
like mass,  there  is  no  doubt  cherry  gum.  If  practically  soluble,  the 
solution  is  mixed  with  excess  of  potash  and  a  little  copper  sulphate, 
gently  heated  and  filtered  : 
(a\  The  filtrate  is  treated  for  dextrin  according  to  9. 
(£)  Precipitate  is  treated  as  described  in  10.  The  deposit  will 
either  agglomerate  and  float,  or  remain  suspended  in  the  fluid.  In 
the  first  case  there  is  gum  arabic,  and  the  original  fluid  will  turn 
amber-yellow  with  potash.  In  the  second  case  if  there  is  no  color 
got  with  potash,  there  is  only  gum  Senegal. 
It  has  been  said  gum  Senegal  is  more  hygroscopic  than  gum 
arabic.  To  make  sure  the  author  dried  both  specimens  at  105 0  C, 
and  then  exposed  them  for  twenty-four  hours  to  moist  air,  when 
gum  arabic  was  found  to  be  even  a  trifle  more  hygroscopical  than 
the  gum  Senegal. 
Camphoric  Acid  was  found  by  Dr.  Leu  (  Wiener  Medic.  Blatter)  to  give  bet- 
ter results  than  atropine  in  cases  of  night-sweats  due  to  phthisis.  The  average 
dose  was  2  gm.,  given  about  noon,  and  2  to  3  gtn.,  given  at  night.  In  some 
cases,  4  or  5  gm.  were  given,  usually  in  capsules,  though  the  taste  is  not 
unpleasant.    The  after-effects  are  quite  insignificant. 
