388 
LIQUOR  AMMONliE  ACETATIS. 
tion,  are  alkaline  to  test  paper,  hence  test  paper  cannot  be  used 
to  determine  the  point  of  saturation.  There  is  also  another 
objection  to  using  test  paper ;  so  much  of  the  carbonic  acid  may 
be  absorbed  by  the  solution,  as  to  give  an  acid  reaction  even 
■when  the  solution  is  alkaline,  as  may  be  proved  by  setting  the 
mixture  aside  for  a  few  hours.  If  test  paper  is  now  applied,  an 
alkaline  reaction  is  at  once  manifested,  and  the  solution  has  a 
distinctly  ammoniacal  odor  and  taste. 
To  remedy  this  source  of  fallacy,  it  has  been  recommended  to 
heat  the  solution,  but  here  there  is  danger  of  error  also,  for  if 
the  heat  be  too  long  applied  it  drives  off  the  ammonia,  and  a 
binacetate  is  the  result. 
These  are  difficulties  which  every  one  will  experience,  who 
observes  carefully  while  making  this  preparation. 
As  often  kept  in  the  shops  it  is  not  liquor  ammonite  acetatis, 
but  a  mixture  of  it,  and  carbonate  of  ammonia. 
There  are  two  ways  in  which  this  remedy  may  be  prepared  so 
as  to  obviate  the  difficulties  above  mentioned;  both  methods  I 
have  tried,  and  they  each  yield  perfectly  satisfactory  results. 
One  method  is  to  neutralize  the  acetic  acid  with  carbonate  of 
ammonia  before  diluting  it  with  the  water,  the  other  is  to  neu- 
tralize diluted  acetic  acid  with  aqua  ammoniae. 
By  adding  carbonate  of  ammonia  to  undiluted  acetic  acid  (No. 
8,)  the  point  of  saturation  is  easily  determined.  This  plan  gives 
a  concentrated  solution  of  the  acetate,  which  dissolves  the  car- 
bonate but  very  slightly  after  it  is  once  saturated,  and  no  car- 
bonic acid  is  held  in  solution.  When  making  it  from  undiluted 
acetic  acid  the  carbonate  may  be  added  until  effervescence  ceases, 
and  then  dilute  it  with  pure  water  free  from  lime. 
It  may  be  prepared  from  aqua  ammonite  by  diluting  the  acid 
to  half  its  usual  strength,  as  allowance  must  be  made  for  the 
water  of  the  aqua  ammonias.  After  the  acid  is  thus  diluted, 
carefully  add  the  water  of  ammonia  until  the  solution  is  neutral 
to  test  paper,  and  dilute  to  its  proper  strength. 
A  few  drops  of  acetic  acid  may  be  added  with  advantage,  if 
the  solution  is  to  be  kept,  though  it  is  always  better  to  prepare 
it  as  it  is  dispensed.  If  kept,  free  carbonate  of  ammonia  is  soon 
generated,  and  the  mixture  becomes  alkaline. 
