Am.  Jour.  Pharm. 
Oct.,  1877 
Laboratory  Notes. 
489 
distinct  brownish  tint,  with  resulting  turbidity  ;  one-50,oooth,  a  distinct 
brownish  precipitate.  As  our  test  was  made  with  100  grams  of  the 
sugar,  it  must  be  safe  to  put  the  limit  of  detection,  for  white  sugars,  at 
one  part  of  lead  oxide  to  200,000  parts  of  solution  (about  66,000  parts 
of  sugar),  a  proportion  giving  one  grain  of  metallic  lead  to  about  10  lbs, 
of  sugar.    No  lead  was  found  in  any  of  the  samples. 
2.  The  test  for  arsenic  was  made  by  Marsh's  operation,  with  use  of 
sodium-amalgam  in  alkaline  solution  of  the  sugar,  the  gas  being  received 
for  some  time  upon  paper  charged  with  silver  nitrate.  A  florence  flask 
of  about  500  cc.  capacity  was  fitted  with  a  cork  admitting  a  tube  of 
about  one-half  inch  diameter.  A  solution  of  100  grams  of  sugar, 
made  slightly  alkaline  with  potassa,  was  put  in  the  flask  and  diluted  to 
fill  it  up  to  the  neck,  sufficient  sodium-amalgum  was  added,  a  disk  of 
filtering  paper  of  about  an  inch  diameter  and  previously  wetted  with 
silver  nitrate  solution  was  placed  over  the  tubule  of  the  cork,  in  place, 
and  the  paper  covered  with  a  watch-glass.  The  flask  was  left  undis- 
turbed, with  constant  slow  evolution  of  hydrogen,  several  hours.  First, 
ordinary  sugars  (supposed  to  be  free  from  poison)  were  subjected  to  the 
operation,  and  it  was  found  that  no  reduction  of  silver  or  blackening  of 
the  paper  occurred.  Next,  different  proportions  of  a  thousandth- 
normal  solution  of  arsenious  oxide  were  added  to  the  sugar  solution, 
in  successive  experiments,  until  it  was  found  that  one-fifth  cc.  of  the 
arsenic  solution  was  the  least  quantity  that  would  cause  a  distinct  and 
unmistakable  blackening  of  the  silver  paper.  Each  cc.  of  the  arsenic 
solution  contained  0*000198  gram  of  arsenious  oxide,  or  0*00015  gram 
of  arsenic  (as  an  element).  The  one-fifth  cc.  contained  0*00003  gram 
of  arsenic,  and  this  quantity  amounts  to  0*00003  Per  cent«  °f  trie  100 
grams  of  sugar  taken.  This  percentage  gives  one  grain  of  arsenic  in 
476  lbs.  of  sugar,  a  limit  of  identification  which  must  be  beyond  the 
limit  reached  through  a  destruction  of  the  organic  matter.  Finally, 
all  the  samples  were  tested  as  above  described,  and  no  arsenic  was 
found  in  any  of  them.  (It  should  be  remarked  that,  had  blackening 
occurred,  it  alone  would  not  have  been  conclusive  evidence  of  the 
presence  of  arsenic.) 
3.  The  ash,  by  ordinary  systematic  qualitative  analysis,  revealed  no 
other  constituents  than  sodium,  potassium,  calcium,  magnesium,  alu- 
minium and  iron  compounds,  and  sulphates,  chlorides,  carbonates  and 
silica.    No  zinc  cr  tin  was  found.    The  ash  of  Syrup  No.  1  consisted 
