174 
Presence  of  Lead  in  Citrates. 
/Am.  Jour.  Pharm. 
\       April,  1894. 
The  same  result  was  obtained  if  the  metallic  particles  were  boiled 
with  a  solution  of  the  acid,  showing  that  the  metal  is  acted  upon  by 
the  acid. 
Another  source  of  the  presence  of  lead  in  citric  acid,  although 
not  in  the  metallic  state,  may  possibly  be  the  commercial  sulphuric 
acid  used  in  its  preparation  from  calcium  citrate. 
The  presence  of  lead  sulphate  in  oil  of  vitriol  is  well  known. 
The  Presence  of  Lead  in  Citrates. — Having  occasion  to  dissolve  a 
large  amount  of  potassium  citrate  in  water,  the  writer  noticed  that 
this  salt  also  deposited  particles  of  the  metal. 
This  was  the  case  in  5  different  samples,  of  which  3  were  obtained 
from  the  same  wholesale  firm. 
The  size  of  these  particles  varied,  in  some  instances  being  the 
same  as  those  usually  found  in  commercial  citric  acid,  while  in 
others  it  was  found  to  be  finely  powdered,  at  times  being  scarcely 
perceptible. 
But  if  the  grayish  sediment,  in  which  form  the  metal  is  found 
occasionally,  was  acted  upon  by  nitric  acid  and  reagents  subse- 
quently applied,  its  nature  was  readily  revealed. 
The  source  of  the  metal  was  doubtless  due  to  the  impure  condi- 
tion of  the  acid,  with  omission  by  the  manufacturer  to  filter  the 
solution  after  saturation,  and  before  evaporating. 
It  may  also  be  possible,  however,  that  concentration  and  granula- 
tion of  the  salt  was  performed  in  lead-lined  vessels. 
The  presence  of  metallic  lead  in  citrates  is  perhaps  of  little  signi- 
ficance, as  long  as  it  remains  in  this  state,  but  it  becomes  of  graver 
importance,  if,  in  some  manner,  it  is  dissolved  and  contaminates  the 
salt. 
Such  is,  in  many  instances,  actually  the  case. 
Before  the  result  of  the  examination  of  commercial  citrates  is  con- 
sidered, the  action  of  an  aqueous  solution  of  potassium  citrate  under 
different  conditions  upon  metallic  lead  may  be  inquired  into. 
To  determine  this  action,  the  following  series  of  experiments  was 
undertaken. 
A  solution  of  the  salt  was  prepared  by  saturating  carefully  selected 
crystals  of  citric  acid,  dissolved  in  distilled  water,  with  potassium 
bicarbonate.  The  resulting  neutral  solution  was  tested  for  lead  with 
a  negative  result. 
It  was  then  divided  into  three  parts : 
