4o8 
Calcium. 
Am.  Jour.  Pharm. 
June,  1920. 
Discussion  of  Method  No.  8.  The  results  obtained  by  this 
method  indicate  that  calcium  can  be  precipitated  quantitatively  as 
oxalate  from  a  slightly  acid  solution.  The  acidity  of  the  solution  is 
due  solely  to  the  presence  of  oxalic  acid  which  is  liberated  by  the  slight 
excess  of  hydrochloric  acid  or  acetic  acid  present  in  the  solution. 
This  fact  is  made  use  of  by  Meade  for  the  rapid  determination  of 
calcium  in  cement  without  previous  separation  of  silica  and  ferric 
and  aluminum  oxides.  The  method  described  by  Meade  is  essentially 
as  described  above  with  the  following  exceptions :  The  acid  solution 
of  the  cement  is  rendered  just  alkaline  with  ammonia  and  then  lo 
Cc.  of  a  lo  per  cent,  solution  of  oxalic  acid  is  added  to  render  the 
mixture  acid  and  redissolve  the  hydroxides  of  iron  and  aluminium 
which  are  partially  precipitated  when  the  mixture  is  rendered  alka- 
line with  ammonia.  In  order  to  test  the  value  of  Meade's  method  a 
sample  of  limestone  yielding  the  following  analysis  by  Method  No. 
7  was  employed  as  a  standard: 
Si02   3  320 
3.300  Av.,     3 .310  per  cent. 
FeiOs-Al'iOs   1.030  Dup.,    i  .030  per  cent. 
CaCOs   77  130 
77.125  Av.,    77 . 127  per  cent. 
MgCOs   18.377 
18.332  Av.,    18.355  per  cent. 
Total.,  99.822  per  cent. 
Meade's  method  was  applied  in  detail  to  a  sample  of  this  lime- 
stone with  the  one  exception  that  the  calcium  oxalate  was  finally 
weighed  as  calcium  sulphate  according  to  Method  No.  6,  instead  of 
being  titrated  by  permanganate  as  required  in  Meade's  Method. 
The  yield  of  CaCOs  was  77.18  per  cent.  Another  assay  was  made 
using  acetic  acid  to  dissolve  the  limestone  and  a  yield  of  77.31  per 
cent.  CaCOs  was  obtained. 
No.  9.  Liberation  of  CO2  by  dilute  hydrochloric  acid  and  calcu- 
lating loss  of  CO2  into  terms  of  CaCOa. 
The  apparatus  known  as  "Geissler's  new  form  carbonic  acid  de- 
termination apparatus,"  listed  on  page  103  of  the  catalogue  of  Eimer 
and  Amend,  New  York,  was  employed. 
The  method  consists  of  treating  a  weighed  sample  of  the  calcite 
in  the  apparatus  with  dilute  hydrochloric  acid  and  drawing  the 
liberated  CO2  through  the  sulphuric  acid  compartment  of  the  appa- 
