306  The  U.S. P.  Inorganic  Chemicals.      { Am,ju°i^im rm' 
Gutzeit  tests  were  given  as  alternate  methods,  the  latter  being  in- 
tended more  particularly  for  the  testing  of  reagents. 
While  absolute  freedom  from  arsenic  is  neither  attainable  nor 
desirable,  yet  under  no  circumstances  should  consideration  of  com- 
mercial advantages  as  to  the  cheapness  or  the  convenience  of 
manufacturers  deter  us  from  guarding  most  carefully  public  health 
and  safety.  It  is  conceded  by  all  that  arsenic  is  present  in  infini- 
tesimal traces  in  almost  every  chemical  and  article  of  food,  hence  it 
remains  for  us  to  discriminate  between  preventive  and  non-preventive 
contamination  as  to  the  limits  permissible.  While  numerous  cases 
of  arsenical  poisoning  through  chemicals  and  food-stuffs  have 
occurred  recently  in  England,  and  a  repetition  in  this  country  is  not 
probable,  yet  we  must  not  overlook  this  possibility  in  important 
chemicals.  As  all  are  aware,  this  trouble  arose  through  the  em- 
ployment of  arsenical  pyrites  in  the  manufacture  of  sulfuric  acid. 
Dr.  Hehner  {Jour.  Soc.  Chem.  Ind.,  1901,  188)  has  estimated  that 
no  less  than  1,800  tons  of  arsenous  acid  are  distributed  in  the  one 
million  tons  of  sulfuric  acid  annually  produced  in  England.  This 
acid  is  employed  directly  or  indirectly  in  the  preparation  of  all  acids 
and  hundreds  of  chemicals,  among  which  we  find  glycerin,  glucose, 
borax,  boric  acid,  ferrous  sulfate  and  preparations  made  from  it, 
sodium  phosphate,  sodium  and  potassium  carbonate  and  acetate, 
phosphorus,  phosphates,  hypophosphites,  etc. 
Based  on  an  extensive  experience  in  arsenic  testing,  Dr.  Hehner 
considers  that  a  sample  of  sulfuric  acid  may  be  considered  as  de- 
arsenicated  if  it  contains  not  more  than  1  part  of  arsenous  acid 
(As203)  in  200,000  (0-0005  per  cent.)  ©r  0-05  milligramme  in  10 
grammes.  (No  difficulty  has  been  found  in  obtaining  samples  of 
acids  of  American  source  which  withstood  the  Marsh  test  for  fifteen 
minutes.) 
British  chemists  have  generally  agreed  upon  fixing  the  limit  at 
o-ooi  gramme  of  As203,  to  the  gallon  for  beverages,  or  pound  for 
foods  (Jour.  Soc.  Chem.  Ind.f  1901,  193,  et  seq.),  corresponding  to  1 
part  in  about  450,000. 
As  to  chemicals,  the  Phar.  Br.  demands  practically  entire  freedom, 
which  certainly  is  entirely  too  stringent  when  arsenic  can  be  demon- 
strated to  the  seventh  place  of  decimals.  Dr.  Curtman  (in  the 
Pharm.  Rundschau,  1891,  p.  175)  placed  a  limit  (U.S.P.,  1890)  of 
per  cent.,  which  would  be  equivalent  to  1  part  of  arsenous 
