june,^?92b^''^'°'  }      Calcium  Carbonate  in  Medicine.  391 
CALCIUM  CARBONATE  IN  PHARMACY  AND  MEDICINE. 
By  ADI.EY  B.  Nichols,  Phar.D., 
PHIIvADEl^PHIA,  PA. 
Chalk,  chemically  mainly  calcium  carbonate,  is  the  name  given 
to  any  soft,  pulverulent,  pure  white  limestone.  The  word  chalk  is 
an  old  one,  having  its  origin  in  the  Saxon  "cealc,"  and  the  hard  form 
"kalk"  is  still  in  use  in  some  districts.  The  German  word  *'Kalk" 
comprehends  all  forms  of  limestone,  and  therefore  a  special  term 
"Kreide"  is  employed,  French  *'Craie." 
Chalk  is  used  extensively  in  a  great  many  ways.  It  enters  into 
the  manufacture  of  cement  and  other  commercial  articles;  it  finds 
a  place  in  various  chemical  processes,  and  in  the  making  of  paint, 
crayons  and  tooth  powders.  Whiting,  or  Spanish  white,  which  is 
used  to  polish  glass  and  metal,  is  purified  chalk,  prepared  by  elutria- 
tion.  Chalk  is  employed  to  some  extent  medicinally,  sometimes  as 
a  mild  astringent,  but  more  usually  for  its  mechanical  action  as  in 
grey  powder,  or  in  chalk  mixture  where  it  produces  its  effect  by 
coating  the  walls  of  the  stomach  and  intestines. 
At  the  present  time,  most  of  the  calcium  carbonate  used  in  med- 
icine is  obtained  from  natural  deposits,  of  which  there  are  a  few  in 
the  United  States,  while  the  largest  deposits,  in  the  form  of  whole 
mountain  ranges,  with  huge  white  chalky  cliffs,  are  found  in  south- 
ern England  and  extending  directly  across  the  channel  and  through 
northern  France.    This  natural  chalk  is  called  creta  alba. 
Calcium  carbonate  is  official  in  two  different  forms  in  the  present 
U.  S.  Pharmacopoeia,  as  Calcii  Carbonas  Praecipitatus,  so-called 
precipitated  chalk,  and  as  Creta  Praeparata,  so-called  prepared  chalk. 
The  precipitated  article  is  prepared  by  interaction  between  calcium 
chloride  and  sodium  carbonate,  calcium  carbonate  being  precip- 
itated. This  differs  physically  from  prepared  chalk,  which  is  native 
chalk  prepared  by  elutriation,  in  that  the  particles  are  more  gritty 
and  it  is  not  usually  so  near  white  in  color,  and  also  lacks  the  ad- 
hesive qualities  which  are  so  pronounced  in  prepared  chalk.  The 
precipitated  chalk  is  better  adapted  for  use  in  tooth  powders,  and 
similar  preparations,  on  account  of  its  gritty  character,  while  the 
prepared  chalk  is  used  extensively  in  medicine  as  an  antacid,  be- 
sides being  particularly  well  adapted  for  the  treatment  of  diarrhoea, 
by  reason  of  its  adhesive  properties. 
