138 
ON  ZINC  SULPHO-PIIENATE. 
has  been  operated  on  which  was  not  palpably  pure.  "When  this, 
however,  is  the  case,  the  solution  of  barium  sulpho-phenate  may 
be  decomposed,  without  any  further  operation,  by  the  zinc-sul- 
phate solution,  with  the  precaution  to  retain  some  of  the  first 
solution  in  order  to  meet  an  accidental  excess  of  the  zinc  so- 
lution. For  every  100  parts  of  phenol  operated  upon,  152  parts 
of  crystallized  zinc  sulphate  may  be  added,  of  which  only  one- 
twelfth  may  be  retained  for  further  addition  if  required. 
The  preparation  of  zinc  sulpho-phenate  may  be  facilitated  by 
the  use  of  perfectly  pure  reagents.  When  they  have  been  mixed 
and  combined  in  the  above  stated  proportions  and  process,  the 
warm  solution,  after  having  been  diluted  with  twice  its  bulk  of 
water,  is  gradually  neutralized  with  zinc-oxide  (free  of  oxide  of 
iron).  When  no  more  oxide  is  dissolved  the  warm  solution  is 
allowed  to  cool,  and  is  then  filtered  ;  the  filtrate  is  evaporated  to 
nearly  half  its  original  bulk,  and  is  then  mixed  and  shaken  with 
ten  times  its  volume  of  alcohol  (90 — 92  per  cent,),  and  the  mix- 
ture is  allowed  to  stand  in  a  cool  place  for  several  days.  The 
zinc  sulphate  separates  as  a  powder  ;  the  supernatant  alcoholic 
solution  of  zinc  sulpho-phenate  may  either  be  directly  evaporated 
to  dryness  or  the  alcohol  may  first  be  restored  by  distillation, 
and  the  evaporation  may  then  be  accomplished.  The  residue  is 
white  zinc  sulpho-phenate  of  a  purity  that  it  yields  with  barium 
chloride  but  a  slight  reaction. 
One  equivalent  phenol,  or  phenyl-alcohol,  forms,  with  two 
equival.  monohydrate  of  sulphuric  acid,  a  compound  ether,  sulpho- 
phenic  acid  (C^gH^O,  SO3+ HO,  SO3).  This,  when  combined 
with  barium  oxide,  forms  C12H5O,  SO3  +  BaO,  SO3,*  and,  with 
zinc  oxide,  the  corresponding  zinc  salt.  The  barium  salt,  when 
crystallized  from  its  aqueous  solution,  forms  rhombic  ct'ystals, 
with  three  equivalents  water  of  crystallization  ;  the  zinc  salt, 
when  crystallized,  forms  bright  lamellas,  with  seven  equivalents 
crystallization  water.  The  officinal  salt  derived  by  exsiccation 
is  deprived  of  the  water  of  crystallization ;  it  dissolves  in  two 
parts  water  of  medium  temperature,  and  in  five  parts  alcohol  of 
90  per  cent. 
The  preparation  of  zinc  sulpho-phenate  from  a  not  quite  pure 
^  Nomenclature  and  notation  are  that  of  Dr.  Hager. 
