Ma^ch!^92o:}    Suggestions  for  National  Formulary.  173 
A  satisfactory  method  of  assay,  which  consists  essentially  of  a 
modification  of  direct  titration  of  iodides  by  N/io  silver  nitrate  and 
potassium  sulphocyanide,  is  outlined  in  my  "Laboratory  Notes," 
on  page  175  of  the  19 19  Proceedings  of  the  Annual  Meeting  of  the 
Pennsylvania  Pharmaceutical  Association. 
TINCTURES. 
TINCTURES   FOR   WHICH   NO   PRACTICAI^   CHEMICAL   OR  PHYSIOI.OGIC 
METHODS  OF  STANDARDIZATION  ARE  AVAILABI^E. 
The  remarks  above  under  "fluid  extracts  for  which  no  practical 
chemical  or  physiologic  methods  of  standardization  are  available" 
also  apply  to  these  tinctures. 
Alcohol  Percentages  of  N.  F.  Preparations. — A  list  of  alcohol 
percentages  of  N.  F.  preparations  is  desirable  as  being  of  assistance 
in  preventing  incompatibilities  in  manufacturing  preparations  and 
in  compounding  prescriptions. 
The  Revision  Committee  should  experience  no  difficulty  in  ob- 
taining satisfactory  data  for  the  establishment  of  these  standards 
from  the  laboratories  of  pharmaceutical  manufacturing  companies 
which  exercise  scientific  control  of  manufacture  and  also  from  other 
scientific  sources. 
TEST  FOR  HEAVY  METAI.S. 
The  N.  F.,  4th  edition,  test  for  heavy  metals  makes  no  provision 
for  those  heavy  metals  beyond  the  lead  and  arsenic  groups,  prin- 
cipally zinc.    The  following  modification  is  suggested: 
Between  the  phrases  "and  again  set  aside  for  half  an  hour"  and 
"The  color  produced,  if  any,  etc.",  add  "evaporate  to  dryness. 
Redissolve  residue  in  i  Mil.  of  diluted  hydrochloric  acid,  dilute  with 
10  Mils,  of  water,  filter,  make  the  filtrate  alkaline  with  ammonia 
water,  boil  until  nearly  free  from  ammonia,  filter,  wash  filter  with 
enough  distilled  water  to  obtain  10  Mils,  of  filtrate,  add  i  Mil.  of  am- 
monia water  followed  by  distilled  water  q.  s.  20  Mils,  and  saturate 
with  H2S  gas."  Add  the  phrase  "either  by  the  hydrogen  sulphide 
T.  S.  or  the  H2S  gas,"  after  "The  color  produced." 
Pharmacrutical  Research  Laboratory, 
H.  K.  MuLFORD  Company, 
PhiIvAdeIvPHIA,  Pa. 
