448 
THE  ENGLISH   COMMERCIAL  SODA  TEST. 
indicate.  It  is  certainly  desirable,  for  the  sake  of  scientific 
accuracy,  that  the  correct  equivalent,  31,  should  be  used  in  test- 
ing ;  but,  seeing  that  manufacturers  have  expended  their  capital 
in  plant,  and  made  their  contracts  for  their  various  materials  on 
the  understanding  that  a  product  containing  a  certain  percent- 
age of  soda  would  be  obtained,  and,  seeing  that  there  are  other 
commercial  customs  of  the  trade  still  in  force,  which  tell  as  much 
against  the  manufacturer  as  the  test  does  in  his  favor — such,  for 
instance,  as  that  of  not  charging  for  fractions  of  percentages — it 
is  more  the  province  of  an  association  like  the  Alkali  Manufac- 
turers' Association,  than  that  of  an  analytical  chemist,  to  make 
alterations  in  trade  usages  affecting  such  vast  interests.  Cer- 
tainly, if  any  alteration  be  made  at  all  by  chemists,  it  should  be 
made  in  the  direction  of  scientific  accuracy,  and  not  in  the  con- 
trary direction,  as  in  the  case  to  which  I  have  referred.  The 
error,  I  find,  arises  in  this  way :  The  test-acid  is  made  so  as  to' 
indicate  the  exact  amount  of  soda  according  to  the  new  and  cor- 
rect equivalent,  31 — that  is,  that  40  parts  of  sulphuric  acid 
should  neutralize  53  parts  of  carbonate  of  suda,  equal  to  31  parts 
of  soda. 
To  convert  the  results  obtained  by  this  test  acid  into  the  Eng- 
lish commercial  soda-test,  it  is  incorrectly  assumed  that  the  31 
parts  of  soda  are  equal  to  32 — in  other  words,  that  the  53  parts 
of  carbonate  of  soda  contain  32  parts  of  soda.  This  is  where 
the  error  lies  ;  for,  according  to  the  correct  English  test,  54  parts 
of  carbonate  of  soda,  and  not  53,  contain  32  of  soda ;  and^ 
therefore,  by  the  English  test,  53  parts  of  carbonate  of  soda  con- 
tain only  31*41  of  soda.  By  thus  mixing  up  the  old  and  the 
new  systems  of  equivalents,  a  sample  of  soda-ash  which,  by  the 
correct  English  test,  contains  50-66  per  cent,  would  be  returned 
as  containing  51  61  per  cent,  of  soda.  A  sample  of  caustic  soda 
which,  by  the  correct  English  test,  would  contain  75*0  per  cent, 
of  soda  would,  by  this  erroneous  method,  indicate  76-4  per  cent. 
It  is  only  necessary  to  point  out  this  error  in  order  that  it  may 
be  avoided  and  guarded  against  by  any  of  your  readers  inter- 
ested in  the  buying  and  selling  of  alkalies. 
I  am,  &c.,  John  Pattinson. 
Newcastle-upon-Tyne,  June  7th,  1870. 
— Chem.  News^  Lond,,  June  17,  1870. 
