Am.  Jour.  Pharm.  ) 
September,  1920.  ) 
Book  Reviews. 
687 
This  volume,  full  of  important  information,  takes  up  physical 
and  chemical  reagents,  organic  and  inorganic,  in  alphabetical  order, 
giving  descriptions  of  the  physical  properties,  action  of  light  and  air, 
precautions  to  be  observed  in  storing,  statements  of  uses,  maximum 
limits  of  impurities  and  methods  of  testing;  the  last  generally  in- 
cludes a  quantitative  assay.  The  percentage  purity  of  inorganic 
chemicals  are  not  always  in  accord  with  the  U.  S.  P.  IX. 
The  following  quotations  are  from  the  preface:  "The  state- 
ments of  the  'Maximum  Limits  of  Impurities,'  so  often  recurring 
throughout  the  book,  are  not  the  amounts  of  impurities  present, 
but  are  the  maxima  permissible  in  chemicals  suitable  for  miscel- 
laneous reagent  purposes.  The  reagents  of  the  market  are  fre- 
quently, if  not  generally,  well  below  these  maxima.  The  percentage 
figures  in  which  the  above  limits  are  stated  were  in  part  determined 
by  the  customary  quantitative  tests,  and  to  this  extent  are  accurate ; 
in  part  by  qualitative  tests  in  which  the  reactions  in  unknowns 
are  compared  with  those  in  knowns."  "The  tests  will  insure  good 
reagents  even  though  the  stated  percentages  of  impurities  may  not 
be  entirely  correct." 
Tests  for  impurities  in  most  cases  are  made  directly  with  solu- 
tions of  the  chemicals  and  only  in  comparatively  few  cases  is  the 
precaution  taken  to  remove  substances  which  may  interfere  with 
the  particular  test.  The  test  for  calcium  is  made  in  ammoniacal 
solution  by  addition  of  ammonium  oxalate;  the  test  for  aluminum 
is  made  by  addition  of  ammonia,  consequently  both  of  these  metals 
will  yield  precipitates  in  the  calcium  test;  the  test  for  heavy  metals 
will  serve  to  indicate  individual  metals,  but  if  mixtures  are  present 
the  test  for  the  metals  comprising  the  mixture  must  be  more  or  less 
uncertain.  These  statements  are  made  because  in  the  "Maximimi 
Limits  of  Impurities"  the  percentages  of  individual  metals  are  given 
and  these  figures  were  probably  obtained  by  adding  known  solu- 
tions of  each  metal  to  the  chemical  reagent  and  then  proceeding 
with  the  test.  In  many  cases  the  production  of  a  color  or  turbidity 
proves  the  presence  or  absence  of  the  impurity;  more  detail  should 
be  given  as  to  the  amount  of  reagent  to  be  added  so  that  the  final 
volume  of  the  test  will  be  known,  also  as  to  the  dimensions  of  the 
vessel  in  which  the  test  is  judged.  In  connection  with  the  tests  for 
arsenic  it  may  be  of  interest  to  mention  that  Marsh's  and  Bettendorf's 
tests  only  are  used.  Any  one  using  chemical  reagents  will  find  this 
book  very  valuable.  Frank  X.  Moerk. 
