178  Presence  of  Lead  in  Citrates.        { A^S£;  Se- 
same impurity,  if  care  is  not  observed  in  the  selection  of  the  acid 
as  well  as  in  their  preparation. 
Of  these  the  two  most  important  are  the  solution  of  potassium 
citrate,  and  the  popular  effervescent  solution  of  magnesium  citrate. 
Solution  of  Potassium  Citrate. — This  solution  sometimes  contains 
traces  of  lead,  if  the  acid  employed  in  its  preparation  is  not  per- 
fectly pure. 
The  method  of  preparation  influences  its  presence  to  some  extent. 
If,  as  directed  by  the  Pharmacopoeia,  separate  solutions  of  the 
acid  and  bicarbonate  of  potassium  are  made  and  subsequently  mixed, 
the  finished  preparation  is  usually  not  affected. 
But,  as  it  is  sometimes  hurriedly  prepared,  if  the  acid  and  bicar- 
bonate are  triturated  together,  the  water  gradually  added,  contami- 
nation is  more  likely  to  take  place. 
Repeated  examination  of  solutions,  prepared  in  this  manner, 
showed  the  presence  of  traces  of  lead. 
Prepared  by  the  official  method,  very  slight  or  no  indications  were 
found. 
As  this  preparation  is  a  much-prescribed  diaphoretic  and  febrile 
remedy,  chiefly  employed  in  diseases  of  children,  care  should  be 
observed  in  the  selection  of  the  ingredients. 
The  possibility  of  the  presence  of  lead  may  be  advanced  as  a  rea- 
son for  the  more  frequent  prescribing  of  the  old  neutral  mixture, 
which  unfortunately  has  been  dropped  by  the  new  Pharmacopoeia. 
Solution  of  Magnesium  Citrate. — What  has  been  stated  in  connec- 
tion with  the  previous  solution  is  also  the  case  with  this  popular 
preparation. 
In  some  lots  of  the  solution,  in  which  the  acid  employed  contained 
particles  of  lead,  and  prolonged  contact  took  place,  it  was  also 
detected  in  the  finished  solution  by  reagents. 
To  determine  if  the  source  of  the  impurity  could  possibly  be 
derived  from  elsewhere  than  the  acid,  the  other  ingredients  were 
also  examined  as  to  their  purity. 
The  magnesium  carbonate  answered  the  pharmacopoeial  require- 
ments, and  the  water  employed  was  found  to  be  free  from  lead. 
A  number  of  samples  were  examined,  of  which  several  responded 
to  the  hydrogen  sulphide  test. 
Some  gave  no  reaction,  showing  the  absence  of  the  metal. 
This  preparation,  if  lead  should  be  present,  contains  only  a  trace, 
