470  Purity  of  Commercial  Aspirin.      {  Am*  j{Sy%JJ^' 
the  standard  for  matching;  therefore  the  two  tablets  =  0.9  Mgm. 
of  free  salicylic  acid  and  consequently  one  tablet  (5  grs.  or  324 
Mgm.)  =0.45  Mgm.,  or  0.14  per  cent,  on  the  presumed  aspirin  con- 
tent. In  bad  cases  it  may  be  necessary  to  make  a  dilution  of  one 
tablet  and  take  an  aliquot  part  of  that,  say,  a  fifth  or  even  a  tenth. 
The  following  quantities  have  been  found:  (a)  0.12  per  cent., 
(&)  0.16  per  cent.,  (c)  1.85  per  cent.,  (d)  0.14  per  cent.,  (e)  0.185 
per  cent.,  (/)  0.06  per  cent.  Samples  (a)  to  (d)  are  well-known 
brands  of  which  (c)  lays  claim  to  a  very  high  excellence  in  common 
with  the  others;  (e)  is  a  "chemist's  own  label"  variety;  and  (/) 
occurs  in  trade  without  advertisement.  Aspirin  from  the  same 
source  as  (e)  is  shown  as  (2)  in  the  acetylsalicylic  acid  table  on 
page  — .  As  to  the  limit  of  free  acid  allowable,  0.2  per  cent,  would 
cover  all  reasonable  requirements  and  permit  a  small  margin  for 
deterioration  due  to  the  manipulation  required  in  preparing  the 
tablet  mass. 
The  following  table  gives  the  analytical  figures  for  five  samples 
selected  from  different  sources:  The  "values"  are  Cc.  JV/5  per  1 
gram  of  the  powdered-tablet  mass  just  as  in  the  case  of  the  acid 
itself,  the  assay  being  on  the  alcoholic  extract. 
No. 
Weight, 
Grains. 
Acid 
Value. 
Ester 
Value. 
1 
Bromine 
Value. 
Free  Salicylic 
Acid,  Per 
Cent. 
Aspirin. 
p     _         1  Per  Tablet, 
PerCent.   |  Grains. 
Ash,  Per 
Cent. 
I 
5.60 
23-73 
23-44 
23.91 
0.12 
86.08 
4.82 
None 
2 
5-66 
24.62 
24.48 
0.12 
88.15 
4.98 
2.25 
3 
5-50 
25-25 
25-17 
25.IO 
Mere  trace 
90.36 
4-97 
4-54 
4 
5-46 
21.63 
22.98 
21.78 
Full  react. 
78.41 
4.28 
7.20 
5 
5-17 
18.48 
20.03 
{  19-59 
72.0 
3-73 
3-io 
(approx.) 
(approx.) 
Number  (1)  is  a  semi-proprietary,  (2)  is  from  a  wholesale  house, 
and  (3)  from  a  firm  of  tablet-makers.  Numbers  (4)  and  (5)  are 
examples  of  very  inferior  products,  the  last-named  being  obviously 
fraudulent. 
It  should  be  pointed  out  that  the  difficulty  with  aspirin  is  one  of 
theory  and  practice.  Acetylsalicylic  acid  is  a  definite  chemical  sub- 
stance, but  in  the  process  of  manufacture  the  difference  of  tech- 
nique employed,  together  with  the  possibilities  for  secondary  reac- 
tions, results  in  the  production  of  an  aspirin  that  departs  fractionally 
from  theory.    If  a  manfacturer  is  producing  a  chemical  which  does 
