THE  PROPER  STRENGTH  OF  FLUID  EXTRACTS. 
295 
may  then,  after  due  washing  with  alcohol,  be  dried  and  used  in 
the  pulverulent  form.  When  alcohol  is  added  in  excess  to  a 
solution  of  the  medicinal  carbonate  the  bicarbonate  precipitates 
in  a  crystalline  form. 
When  a  saturated  solution  of  sesqui-carbonate  of  ammonia  in 
water  is  saturated  with  COg,  a  quantity  of  the  bi-carbonate  sep- 
arates in  crystals,  owing  to  its  less  solubility. 
The  translucent  lumps  of  sesqui-carbonate  of  ammonia  when 
exposed  lose  much  weight,  and  the  residue  is  almost  entirely  bi- 
carbonate. This  is  the  form  in  which  it  is  most  usually  met 
with,  and  it  may  be  obtained  from  that  salt  at  any  time,  but  it  is 
too  expensive,  100  parts  of  the  officinal  carbonate  yielding  only 
about  50  parts  of  the  bicarbonate  instead  of  59,  the  theoretical 
yield.  The  relative  proportions  of  the«potash  soda  and  ammonia 
salts  to  saturate  one  equivalent  of  SO3  are  100,  84  and  70,  so 
that  ten  parts  of  bicarbonate  ammonia  nearly  equal  14J  parts 
of  the  potash  and  12  of  the  soda  salt. 
THE  PROPER  STRENGTH  OF  FLUID  EXTRACTS. 
By  William  Procter,  Jr. 
The  idea  of  fluid  extracts  being  grain  to  minim  in  proportion  is 
a  beautiful  one,  enabling  all  to  remember  their  medicinal  strength. 
The  only  officinal  departures  from  this  ratio  are  those  of  wild 
cherry  and  cinchona.  The  former,  owing  to  the  peculiar  char- 
acter of  the  process,  cannot  be  made  more  concentrated  with  a 
certainty  of  exhausting  the  material.  The  latter  probably  can 
be  made  to  conform  by  the  agency  of  glycerin.  Originally 
buchu,  valerian  and  several  others  were  in  the  same  proportion, 
but  were  raised  to  the  full  strength  in  1860.  In  the  case  of 
rhubarb,  the  large  amount  of  soluble  matter  in  the  root  is  incom- 
patible with  so  much  sugar  as  exists  in  the  officinal  recipe,  not 
only  because  the  preparation  is  too  thick  in  consistence,  but  the 
small  quantity  of  alcohol  retained  in  the  extract  favors  the  crys- 
tallization of  the  sugar.  This  may  be  avoided  by  substituting 
glycerin  for  sugar,  with  perfect  success,  as  recommended  by  Mr. 
A.  B.  Taylor  (Proc.  A.  P.  Assoc.  1865,  p.  156),  which  I  have 
recently  tried  with  success. 
