^*"*5ec?";iS*'"™-}       Commercial  Sodium  Bicarbonate,  603 
bicarbonate  of  sodium,  15  of  which  are  commercial  products  and  one 
was  marked  chemically  pure.  The  samples  were  procured  from  dif- 
ferent sources,  constituting  the  most  universally  known  brands.  Nos. 
1  to  8  inclusive,  are  of  American  manufacture,  No.  8  being  the  C.  P. ; 
Nos.  9  to  14  inclusive  are  English,  and  Nos.  15  and  16  are  French 
products. 
The  requirements  of  the  Pharmacopoeia  were  executed  with  each 
sample,  and  compared  to  classify  them. 
None  of  the  samples  on  agitation  with  water  left  an  insoluble  resi- 
due. It  is  stated  that  the  salt  on  continued  heating  loses  moisture 
and  carbon  dioxide,  amounting  to  about  37  per  cent,  by  weight.  This 
percentage  will,  of  course,  vary  with  the  moisture  present,  and  also 
the  amount  of  total  NaHCOg.  While  estimating  with  each  sample,  as 
will  be  shown  later,  the  total  loss  on  ignition  was  noted,  and  is  as  fol- 
lows: 
No.  (1),  36-36  per  cent.  ;  (2),  36*33  per  cent. ;  (3),  35*76  per  cent. ; 
(4),  36-12  per  cent.  ;  (5),  36*66  per  cent.;  (6),  36*28  per  cent.  ;  (7), 
36-30  per  cent.  ;  (8),  36-78  per  cent. ;  (9,)  36*  per  cent.  ;  (10),  36*80 
percent.;  (11),  36*65  per  cent.  ;  (12),  36*40  per  cent.  ;  (13),  36*54  per 
cent.;  (14),  35*78  percent.;  (15),  36*09  percent.;  (16),  3(5*33  per 
cent. 
For  the  detection  of  chlorides,  a  1  per  cent,  aqueous  solution  of  the 
salt  was  supersaturated  with  HNO3,  and  then  AgNOg  added.  Only 
a  slight  opalescence  was  produced,  and  with  most  of  them  hardly  per- 
ceptible. For  sulphates  another  portion  was  similarly  tested  with 
BaClg,  showing  but  traces  present  in  most  cases.  On  heating  a  small 
portion  with  sodium  hydrate,  two  samples,  Nos.  5  and  10,  gave  evi- 
dence of  ammonia,  the  others  were  free  from  same.  No.  5  was  man- 
ufactured by  the  Solvay  or  ammonia-soda  process,  and  No.  10  was  of 
English  manufacture,  and  probably  by  the  same  process. 
For  the  limit  carbonate  the  following  test  was  applied  as  directed  : 
2  gms.  of  the  salt  were  dissolved  in  30  cc.  of  cold  water,  and  then 
added  to  a  5  per  cent,  aqueous  solution  of  mercuric  chloride.  In  the 
absence  of  more  than  about  3  per  cent,  of  carbonate  a  white  cloud 
should  form  only,  but  neither  a  red  precipitate  nor  a  red  color  should 
make  its  appearance  within  3  minutes.  According  to  this  reaction, 
Nos.  1,  2,  7,  8,  9,  11,  13  and  16,  gave  either  no  precipitate,  or  only  a 
white  cloud.  Nos.  3,  4,  6, 12, 14  and  15  gave  either  a  light  red  color 
or  a  precipitate.    Nos.  5  and  10  gave  a  decided  white  precipitate,  but 
