134     SULPHO-CARBOLIC  ACID  AND  THE  SULPHO-CARBOLATES. 
Siilplio-carbolate  of  Soda. — Having  had  occasion  to  prepare 
this  salt  several  times  in  quantities  varying  from  a  few  ounces  to 
more  than  a  pound,  we  have  used  the  following  formula,  which 
is  very  easily  carried  out,  and  may  be  found  useful  where  this 
salt  is  needed  to  be  made  promptly,  viz.  : 
Take  of  Pure  Crystallized  Carbolic  Acid  (Calvert's). 
Sulphuric  Acid  (1-84  sp.  gr.)  16  troyounces. 
.   Distilled  Water,  three  pints. 
Crystallized  Carbonate  of  Soda,  a  sufficient  quantity. 
Melt  the  carbolic  acid  in  a  bath  of  w^arm  water  and  mix  it 
with  the  sulphuric  acid  gradually  added  in  a  quart  flask.  Con- 
siderable heat  is  developed,  which  is  increased  bj^  using  direct 
heat  until  the  temperature  attains  280°  Fahr.  It  is  then 
allowed  to  stand,  in  a  warm  place,  for  12  hours.  Dissolve  in 
the  water,  set  aside  a  fiuidounce  of  the  solution  and  add  the 
carbonate  of  soda,  previously  powdered,  with  constant  stirring 
until  saturation  is  approached,  then  proceed  cautiously,  to  avoid 
an  excess  of  alkali  which  deepens  the  rose  color,  using  the  re- 
served solution  to  insure  its  correction  if,  by  accident,  the  so- 
lution is  alkaline.  (An  advantage  has  been  derived  from  using 
the  bicarbonate  of  soda  in  the  carbonate.) 
The  solution  is  now  filtered,  evaporated  at  150°  Fahr.  to 
three  pints,  and  set  aside  where  it  will  cool  slowly  for  24  hours, 
to  crystallize.  The  crystalline  crusts  should  be  broken  up  so  as 
to  drain  in  a  glass  funnel,  and  washed  with  a  little  ice  cold 
water  to  remove  the  colored  mother  water,  and  then  dried  on 
bibulous  paper,  unless  desired  quite  colorless,  when  it  should  be 
dissolved  in  hot  water  and  again  crystallized  ;  but  for  all  ordi- 
nary medical  use  the  first  crystallization,  which  amounts  to  about 
22  ounces,  is  sufficiently  pure,  whilst  the  entire  amount  of  the 
salts  formed  is  more  than  37  ounces.  With  the  greatest  care 
there  appears  to  be  free  sulphuric  acid,  consequently  sulphate 
formed,  which  is  a  great  objection  to  the  direct  process  for  mak- 
ing the  soda,  zinc,  and  magnesia  salts.  Sulpho-carbolate  of 
soda  crystallizes  in  colorless  rhombic  prisms,  and  are  permanent 
in  the  air,  though  containing  water  of  crystallization.  For  this 
reason  the  mixed  crystals  of  sulphate  and  sulpho-carbolate  are 
easily  distinguished  on  exposure,  the  former  efflorescing.    It  is 
