308 
STRENGTH  OF  DILUTED  ACETIC  ACID. 
will  be  L2ii  —1.0059.  And  this  is  doubtless  the  strength  intended 
by  the  Pharmacopoeia ;  the  mistake  was  made  in  ordering  the 
acetic  acid  of  31  per  cent,  to  be  one-seventh  of  the  water  in- 
stead of  one-seventh  of  the  mixture.  On  page  20  of  the  U.  S. 
Dispensatory,  11th  edition,  the  strength  of  the  dilute  acetic  acid 
is  given  as  3  per  cent.,  on  page  840  as  4.5  per  cent,  of  the  mono- 
hydrated  acid ;  this  latter,  or  rather  a  somewhat  stronger  acid, 
is  obtained  by  the  above  proportions.  The  fluidounce  of  an  acid 
of  1.006  weighs  455.6944  x  1.006  =458.43  grs.,  which,  if  of  4.58 
per  cent.,  contain  20.97  grs.  HO,  C4  H3  03.  The  147  grains 
of  the  monohydrate  of  one  fluidounce  of  acetic  acid  spec.  grav. 
1.041  are  distributed  among  7  fluidounces  of  the  mixture,  thus 
giving  to  each  21  grs.  of  this  monohydrate,  which  saturate  21*^°? 
=  35.7  grains  of  bicarbonate  of  potassa,  2^=17.5  grs.  carbon- 
ate of  lime,  and  22^L  —5.95  grs.  dry  ammonia,  producing  21+5.95 
=  26.95  grains  dry  ammonia.  100  grains  of  this  dilute 
acid  are  sufficient  to  saturate 1Q0x21xl0Q-2— 7.65  grs.  of  bicarbonate 
458.43x60  ° 
of  potassa,  and  100x21xi°— 3.81  grs.  carbonate  of  lime.    If  the 
r  7  458.43x60  ° 
standard  strength  of  the  acid,  therefore,  is  retained  at  31  per 
cent.,  the  directions  of  the  Pharmacopoeia  ought  to  be  : 
Take  of  acetic  acid,  one  pint ;  distilled  water,  six  pints. 
Mix  them. 
Diluted  acetic  acid  has  the  specific  gravity  1.006,  and  100. 
grains  of  it  saturate  7.6  grains  of  crystallized  bi- 
carbonate of  potassa. 
Subsequently,  on  referring  to  Mr.  Parrish's  «  Practical  Phar- 
macy," I  found  on  page  124  the  statement,  that  "100  grs.  of 
the  officinal  acetic  acid  will  be  accurately  saturated  by  60  grs. 
of  crystallized  bicarbonate  of  potassa."  But  100  grs.  of  the  stand- 
ard  acid  contain  31  grs.  of  the  monohydrate,  which  are  saturated 
by  31xlJ)Q_^=51.77  grs.  0f  bicarbonate ;  an  acid  of  the  saturating 
power  as  stated  by  Mr.  Parrish  is  therefore  above  the  standard 
strength,  for  60  grs.  of  bicarbonate  of  potassa  are  saturated  by 
6^=35.928  grs.  HO,  C4  H3  03,  that  is  by  100  grs.  of  an  acid 
of  36  per  cent.,  which,  according  to  Mohr,  has  a  specific 
gravity  of  1.047.  Such  an  acid,  however,  if  diluted  with  seven 
volumes  of  water  furnishes  a  dilute  acid  of 36xL047  =4.68  per  cent. 
8.047  r 
