Am.  Jour.  Pharm.  \ 
November,  1897.  J 
Official  Lead  Preparations. 
569 
Every  pharmacist  has  undoubtedly  observed  the  physical  and 
chemical  variations  in  commercial  sugar  of  lead.  In  the  price  lists  of 
wholesale  drug  firms  we  find  quoted  several  varieties,  among  which 
we  find  the  white  and  brown.  That  the  latter  has  been  used  in 
making  Goulard's  extract  in  some  instances  was  revealed  by  the 
examination  of  commercial  samples. 
But  not  only  careless  selection  of  the  salt,  but  the  inherent  phys- 
ical properties,  as  well  as  the  liability  of  chemical  change,  have  a 
material  influence,  and  may  either  increase  or  diminish  the  strength 
of  the  preparations  made  therefrom. 
Treating  first  of  the  liability  of  increase,  we  find  that  lead  acetate 
contains  14-25  per  cent,  of  water  of  crystallization. 
The  Pharmacopoeia  states  that  this  is  lost  at  a  temperature  of  40°C, 
and  Ladenburg  states  that  the  salt  loses  its  water  of  crystallization 
in  dry  air. 
As  in  our  climate  the  summer  temperature  falls  but  a  few  degrees 
short  of  the  above  figure,  the  liability  of  the  loss  of  water  must  be 
borne  in  mind. 
This  will  result  in  an  increase  in  the  lead  strength  of  a  salt  thus 
exposed,  and  is,  in  not  a  few  instances,  in  consequence,  the  result 
of  keeping  the  salt  in  packages  in  place  of  well-closed  vessels. 
To  substantiate  this  point,  the  writer  made  the  following  obser- 
vation : 
Goulard's  extract  was  prepared  from  a  specimen  of  lead  acetate 
obtained  from  a  reputable  manufacturer  and  labelled  CP.,  U  S.P.,  put 
up  in  paper  cartoons. 
The  solution  had  the  specific  gravity  of  1-253,  and  13  67  grammes 
•    ,  n 
required  27  c.c.  -  H2S04  for  precipitation. 
But  the  prolonged  exposure  of  the  salt  to  air  is,  on  the  other 
hand,  liable  to  cause  a  decrease  in  the  lead  strength. 
Lead  acetate  absorbs  C02  from  the  atmosphere,  giving  the  salt  a 
white  crust  of  carbonate. 
Prolonged  exposure  results  in  partial  conversion  into  lead  carbon- 
ate, and  as  the  latter  is  insoluble  in  water,  a  deficiency  in  the  lead 
strength  of  the  salt  takes  place. 
This  is  probably  the  cause  of  the  diminished  strength  of  commer- 
cial Goulard's  extract,  and  is  the  result  of  the  not  unusual  procedure 
of  using  the  effloresced,  unsalable  scraps  and  refuse  of  packages  in 
the  sugar  of  lead  drawer. 
