Am.  Jour.  Pharm. 
Dec,  1888. 
Commercial  Sodium  Bicarbonate. 
605 
bicarbonate  is  decomposed  by  heat  into  the  normal  carbonate,  car- 
bon dioxide  and  water.  One  hundred  parts  of  jSIaHCOs  ^^i^l  yield 
63  095  p.  Na^COs,  10-714  p.  and  26-191  p.  CO2.  Knowing 
the  amount  of  COg  produced  by  100  parts  of  NaHCOg,  the  corres- 
ponding percentage  of  total  NaHCOg  in  the  sample  can  be  calculated 
from  the  weighed  products  obtained  by  ignition  in  the  combustion 
tube.  The  total  COg  present  in  the  sample  was  also  estimated  by 
decomposition  with  an  acid  and  noting  the  loss.  The  difference  be- 
tween this  total  CO2  and  the  COj  necessary  for  the  NaHCOs  present 
in  the  sample,  would  indicate  the  amount  of  CO2  in  combination  as 
normal  carbonate,  in  which  form  it  can  easily  be  calculated.  In 
similar  manner  the  amount  of  moisture  was  obtained.  Knowing  the 
theoretical  quantity  of  H2O  produced  from  100  parts  of  bicarbonate 
on  decomposition  by  heat,  the  amount  which  would  be  formed  from 
the  percentage  of  NaHCOg  present  can  then  be  calculated.  The 
difference  between  this  amount  and  the  total  amount  of  H2O  weighed 
on  decomposition,  represents  the  moisture. 
The  ammonia  in  Nos.  5  and  10  was  estimated  by  the  following 
method  : — 
An  aqueous  solution  of  a  weighed  quantity  of  the  salt  was  boiled 
for  some  time  with  solution  of  soda.  The  NH3  liberated  was  con- 
ducted into  a  flask  containing  50  cc.  of  one-tenth  normal  oxalic  acid 
solution.  The  absence  of  any  sodium  hydrate  carried  over  during  the 
process  was  verified  by  the  flame  test.  The  excess  of  oxalic  acid  was 
then  triturated  with  soda  solution  of  same  strength.  The  results 
obtained  were  0*217  per  cent,  and  0*366  per  cent,  of  IS'Hg  for  Nos.  5 
and  10  respectively. 
The  amount  of  chlorides  and  sulphates  was  estimated  in  usual  man- 
ner by  precipitation  with  BaClg  and  AgNOg,  and  weighing  as  BaS04 
and  AgCl. 
The  following  table  gives  complete  analysis  of  each  sample : — 
NaHCOi ..... 
95-68 
96  30 
92-69 
94  92 
95-19 
94-43 
94-92 
97-44 
95-72 
94-43 
95-65 
94-59 
96-41 
94-28 
92-44 
94-85 
Na2  COa-  
2-45 
2-10 
4-50 
3-52 
2-00 
3-58 
2  99 
1-88 
2-98 
2-57 
2-95 
3-79 
2  37 
4-25 
4-91 
3-15 
NaCl  
0-50 
0-34 
0-60 
0-16 
019 
0-04 
0.51 
0-12 
0-33 
0-14 
0-17 
0-05 
0-20 
0-30 
0-02 
0.04 
NaaSOi 
0-40 
0-38 
0-54 
007 
0-05 
067 
0-22 
005 
0-12 
0-02 
001 
0-03 
0.02 
0-13 
0-55 
0-57 
NH4  HCO3 .. 
1-00 
170 
0-89 
0-83 
1-57 
1-27 
1-55 
1-24 
_ 
1-26 
0-47 
077 
107 
113 
0-92 
0-99 
200 
1-33 
99-92 
99  95 
99  90 
99-94 
99-98 
99-96 
99-90 
99-96 
99  92 
99-93 
99-91 
99-94 
99-92 
99-95 
99-92 
99-94 
