384  Report  of  Research  Committee  B. 
REPORT  OF  RESEARCH  COMMITTEE  B. 
To  the  Committee  of  Revision  of  U.  S.  P.,  18 go. 
no.  1. 
By  Dr.  Chas  O.  Curtman. 
Read  before  the  Missouri  Pharmaceutical  Association,  June,  1894. 
A  number  of  experiments  have  been  made  for  the  purpose  of 
ascertaining  the  conditions  most  favorable  to  the  result  of  the  test 
for  arsenic  by  stannous  chlorid  (Bettendorf's  test  and  its  modifi- 
cations). 
The  inquiry  was  directed  to  the  following  points : 
(1)  The  limit  of  sensitiveness  of  the  test  in  its  various  modifi- 
cations. 
(2)  The  best  proportion  of  reagent  to  specimen. 
(3)  The  influence  of  the  use  of  metallic  tin  together  with  the 
stannous  chlorid. 
(4)  The  influence  of  the  presence  of  other  substances  in  the  speci- 
men tested. 
I.  LIMIT  OF  SENSITIVENESS. 
The  following  reagents  were  used : 
(a)  The  solution  directed  for  Bettendorf's  test  by  the  U.  S.  P., 
consisting  of  a  saturated  solution  of  pure  stannous  chlorid  in  pure 
concentrated  hydrochloric  acid.  The  specific  gravity  of  this  solution 
was  =  1-467. 
(b)  Metallic  tin,  perfectly  pure,  in  thin  cylinders,  from  which 
shavings  of  about  o-i  gm.  were  taken  as  needed. 
(c)  Stannous  chlorid  solution  prepared  according  to  the  German 
"  Arzneibuch  "  by  saturating  a  mixture  of  5  parts  of  crystals  of 
stannous  chlorid  and  I  part  of  hydrochloric  acid  with  dry  hydro- 
chloric acid  gas.    The  specific  gravity  was  =  19 12. 
All  of  the  materials  used  were  previously  tested  for  absence  of 
arsenic  by  Gutzeit's  test,  so  as  to  exclude  any  fallacies  arising  from 
the  introduction  of  even  small  traces  of  arsenic  by  the  reagent, 
which  might  cumulate  with  those  in  the  specimen. 
It  was  easy  enough  to  procure  pure  metallic  tin,  but  impossible 
to  obtain  from  local  dealers,  hydrochloric  acid  sufficiently  free  from 
arsenic  to  stand  Gutzeit's  test  for  one  hour ;  so  that  I  had  to  distill 
from  purified  sulphuric  acid  and  pure  sodium  chlorid  the  hydro- 
chloride acid  required  for  the  preparation  of  the  reagents. 
