l82 
Medicinal  Plants  in  Bahia. 
Am.  Jour.  Pharm. 
March,  1920. 
i.  e.,  TOO  Gms.  of  acid  should  become  98.71  Gms.  after  de-arsenica- 
tion,  so  that  the  strength  of  the  sulphuric  acid  in  the  de-arsenicated 
100  X  77  I 
product  should  be  — =78.1  per  cent.    Since  it  was 
98.71 
found  to  be  77.  i,  there  is  an  apparent  loss  of  i  .3  per  cent,  of  the 
sulphuric  acid  originally  present.  This  figure  cannot  be  taken  as 
accurate,  for  absorption  of  water  may  have  occurred,  and,  further, 
it  is  not  possible  in  small  experiments  to  estimate  the  yield  of  de- 
arsenicated  acid  at  all  exactly.  But  it  can  be  taken  that  the  loss  of 
sulphuric  acid  by  reduction  is  less  than  i ,  3  per  cent,  of  the  original 
sulphuric  acid.  The  loss  could  certainly  be  diminished  by  (a) 
using  a  more  efficient  apparatus  for  mixing  the  gas  with  the  acid, 
{h)  stopping  the  treatment  before  the  de-arsenication  had  gone  so 
far  as  the  point  reached  in  the  experiment,  and  (c)  using  a  Glover 
tower  acid  of  more  normal  arsenic  content,  for  all  these  conditions 
would  diminish  the  duration  of  treatment. 
From  these  experiments  it  is  clear  that  for  practically  complete 
de-arsenication  of  acid  of  any  strength  up  to  95  per  cent,  the  only 
essential  condition  is  that  the  acid  after  treatment  must  contain 
dissolved  hydrogen  sulphide,  and  so  long  as  this  condition  is  ful- 
filled the  acid  can  stand  in  contact  with  the  arsenious  sulphide  with- 
out any  serious  increase  of  arsenic  content.  As  soon  as  the  hydro- 
gen sulphide  has  been  destroyed  the  acid  takes  up  arsenic  again 
at  a  rate  depending  upon  its  strength. 
K.  Schmidt  {Arch.  Pharm.,  45:  255,  1917)  states  that  although 
water,  alcohol,  and  dilute  solutions  of  hydrochloric  acid  cause  ap- 
preciable decomposition  of  arsenious  sulphide,  such  decomposi- 
tion is  prevented  by  the  presence  of  small  quantities  of  hydrogen 
sulphide.  The  above  experiments  shows  that  hydrogen  sulphide 
has  a  similar  effect,  even  in  the  presence  of  strong  sulphuric  acid. 
— Royal  HoUoway  College  (University  of  London). 
MEDICINAL  PLANTS  IN  BAHIA.* 
By  Consul  Edward  Higgins, 
bahia,  brazil,  nov.  i,  1919. 
The  State  of  Bahia,  Brazil,  offers  to  the  medical  world  an  abundant 
and  varied  supply  of  plants,  roots,  barks  and  gums,  including  many 
*  From  Commerce  Reports,  Dec.  26,  1919. 
