Am-juiyr;i?97?rm'}      Processes  and  Laboratory  Notes.  353 
misapplied.  Among  these  were  "  C.  P.  chemicals  for  photographic 
purposes,"  as  sodium  thiosulphate  and  sulphite  containing  iron  and 
zinc ;  also  sodium  carbonate  containing  large  quantities  of  chlorides 
and  sulphates.  Fortunately,  instances  of  this  kind  are  rare,  and, 
with  the  exception  of  one  manufacturer  who  evaded  the  question 
by  claiming  that  C.  P.  meant  commercially  pure,  it  has  been  found 
that  chemicals  when  designated  C.  P.  conform  to  these  requirements 
as  closely  as  is  practicable.  In  this  connection,  the  fact  that  even  the 
U.S. P.  is  somewhat  inconsistent  in  its  requirements  for  the  purity 
of  certain  chemicals  may  be  new  to  some  persons.  The  require- 
ments of  the  U.S  P.  for  the  purity  of  carbonate  and  bicarbonate  of 
sodium  allow  a  limit  of  chlorides  and  sulphates  in  each  case.  In 
benzoate,  salicylate  and  other  salts  of  sodium,  which  are 
made  from  one  of  the  first-mentioned  bases,  absolute  free- 
dom from  chlorides  and  sulphates  is  required,  with  no  apparent 
reason  for  such  an  increase  in  the  standard  of  purity ;  the  result 
being  that  the  salts  of  sodium,  such  as  those  mentioned,  are  found, 
in  most  cases,  to  contain  traces  of  chlorides  and  sulphates,  even 
when  labelled  U.S. P.  The  fulfillment  of  such  increased  requirements 
generally  means  an  increase  in  the  cost  of  the  compound,  with  no 
practical  benefit  resulting  therefrom. 
In  criticising  the  quality  of  C.  P.  chemicals,  care  should  be  taken 
not  to  overstep  the  bounds  of  reason,  as  in  a  certain  case  where  a 
bottle  of  C.  P.  ferrous  sulphate  was  returned  after  some  weeks  as  not 
answering  the  tests  for  a  pure  salt.  As  the  bottle  was  only  partly 
filled,  and  loosely  stoppered,  the  complaint  was  unreasonable.  It  is 
easier  to  find  fault  with  an  article  than  it  is  to  make  excuses  for 
any  deficiencies  discovered  ;  but,  for  the  interests  of  commercial  har- 
mony, let  us  avoid  being  hypercritical.  For  use  as  reagents,  chemi- 
cals should  be  required  of  the  highest  standard  possible,  but  for  pre- 
scription use  it  is  unnecessary  to  require  conformity  to  a  standard 
of  purity  which  raises  the  cost  of  the  compound  without  increasing 
its  practical  value. 
A  chart  of  the  Mineral  Products  of  the  United,  States  from  1887  to  1896 
inclusive,  has  recently  been  issued  by  the  U.  S.  Geological  Survey.  The  pro- 
ducts are  divided  into  two  classes,  metallic  and  non-metallic.  The  grand  total 
in  value  of  both  metallic  and  non-metallic  products  amounted  in  1887  to  $520,- 
714,474,  and  gradually  rose  to  $648,670,798  in  1892,  when  it  dropped  off  some 
|74,ooo,ooo  in  1893,  the  values  thereafter  being  somewhat  variable,  and  in  1896 
they  had  risen  to  $611,510,700. 
