1 8  Inorganic  Chemicals  of  the  U.S.P.      { A  jaiuaryPi906rm' 
A  CRITICAL  REVIEW  OF  THE  INORGANIC  CHEMISTRY 
OF  THE  NEW  UNITED  STATES  PHARMACOPCEIA. 
By  Henry  W.  Schimpf. 
{Continued  from  page  562,  December,  1905.) 
THE  INORGANIC  ACIDS. 
Acidum  Boricum  (H3B03). — It  should  be  not  less  than  99*8  per 
cent.  pure.  The  1890  Pharmacopoeia  stated  that  the  solubility  of 
boric  acid  in  water  is  increased  by  the  addition  of  hydrochloric  acid. 
The  new  Pharmacopoeia,  however,  contradicts  this  statement,  and 
declares  that  the  addition  of  hydrochloric  acid  decreases  the  solu- 
bility, which  latter  statement,  according  to  N.  Herz,  Zeits.  Unorg. 
Chem.,33,  335,  is  correct. 
The  tests  for  impurities  are  the  same,  with  the  exception  of  the 
time-limit  test,  for  heavy  metals,  and  the  omission  of  tests  for 
ammonia  and  for  sodium.  A  Voluniettic  Assay  Method  is  given.  In 
this  a  solution  of  boric  acid  in  water  and  glycerin  is  titrated  with 
normal  sodium  hydroxide  V.  S.,  using  phenolphthaiein  as  indicator.1 
The  Diluted  Mineral  Acids  are  all  10  per  cent,  in  strength.  Dilute 
hydrocyanic  acid  is  2  per  cent.  The  strong  mineral  acids  remain  of 
the  same  strength,  except  that  aromatic  sulphuric  acid  which  is  20  per 
cent,  instead  of  18-5  per  cent.,  and  sulphurous  acid  is  64  instead  of 
6  per  cent. 
Acidum  Hydrocyanicum  Dilutum. — The  distillation  method  for  the 
preparation  of  this  acid,  in  which  a  solution  of  potassium  ferrocyan- 
ide  and  sulphuric  acid  were  made  to  react,  has  been  dismissed,  as  it 
should  be.  Very  lew,  if  any,  retail  druggists  have  the  facilities  tor 
manufacturing  an  article  of  this  kind,  and  therefore  its  production  is 
best  left  to  the  manufacturer.  The  alternate  method,  which  was 
official,  as  well,  in  the  old  Pharmacopoeia,  and  by  means  of  which 
the  extemporaneous  manufacture  of  diluted  hydrocyanic  acid  is 
easily  accomplished,  is  now  the  official  process.  In  this  method 
silver  cyanide  is  added  to  diluted  hydrochloric  acid,  the  mixture 
shaken  and  when  the  precipitate  has  settled  the  clear  liquid  is 
poured  off : 
AgCN  +  HC1  =  AgCl  -f  HCN. 
1  Thomson,  J.  S.  C.  L,  xii,  432,  finds  that  the  addition  of  30  per  cent,  or  more 
of  glycerin  in  this  assay  increases  the  susceptibility  of  phenolphthaiein  in 
titrating  boric  acid. 
