Am.  Jour.  Pharm. 
June,  19 18. 
Current  Literature. 
459 
in  1,000,000  if  certain  conditions  can  be  secured.  It  is  pointed  out 
that  if  a  sample  of  water  contains  both  zinc  and  visible  matter  in 
suspension,  most  of  the  zinc  will  be  found  to  be  in  suspension  and 
not  in  solution. 
The  test  with  ammonium  sulphide  is  made  as  follows :  To  100 
Cc.  of  the  sample  contained  in  a  test  mixer,  1  Cc.  hydrochloric  acid 
is  added,  and,  after  shaking,  2  Cc.  of  ammonium  sulphide  solution. 
Simultaneously  100  Cc.  of  zinc-free  tap-water  is  similarly  treated. 
If  at  the  end  of  fifteen  minutes  no  difference  can  be  seen  between 
the  sample  and  the  tap-water,  the  sample  contains  less  than  1  part 
of  zinc  in  100,000.  If  the  sample  develops  a  visible  opalescence,  the 
presence  of  zinc  cannot  necessarily  be  inferred.  A  further  portion 
of  the  sample  must  be  freed  from  iron  and  alumina,  and  then  tested 
as  described  and  the  opalescence  compared  with  that  developed  in 
standard  solutions  of  known  zinc  content. 
The  ferrocyanide  test  should  be  applied  twice  to  waters  carrying 
suspended  matter,  first  to  100  Cc.  of  the  unfiltered  water,  and  then 
to  100  Cc.  of  the  filtered  water.  To  100  Cc.  of  the  sample  1  Cc.  of 
dilute  (1:5)  hydrochloric  acid  is  added,  and  after  a  minute  1  Cc. 
of  a  1  per  cent,  solution  of  potassium  ferrocyanide  not  more  than 
a  few  hours  old.  The  opalescence,  if  any,  produced  is  compared 
with  standards  in  the  usual  manner,  but  to  detect  1  part  in  1,000,000 
or  estimate  larger  quantities  accurately  the  standards  must  be  pre- 
pared from  water  very  similar  except  that  it  is  zinc  free.  Some- 
times the  same  water,  before  contamination  by  zinc,  is  available. 
In  other  cases,  if  the  sample  has  been  analyzed,  an  approximately 
similar  solution  can  be  prepared  artificially.  The  use  of  distilled 
water  for  standards  may  lead  to  over-estimation  of  the  zinc  by  as 
much  as  100  per  cent.  (R.  Meldrum,  Chem.  Nezvs,  1917,  116,  271- 
272,  295-296.    From  The  Analyst.) 
Separation  and  Estimation  of  Lactic,  Succinic,  and  Malic 
Acids  in  Wines. — The  method  of  separation  of  these  acids  from 
other  acids  in  wine  depends  on  their  solubility  in  a  mixture  of 
alcohol  and  ether;  the  acids  are  then  separated  from  one  another 
by  making  use  of  the  different  solubilities  of  their  calcium  salts  in 
alcohol.  Fifty  Cc.  of  the  wine  are  neutralized  with  N/I  potassium 
hydroxide  solution,  and  a  quantity  of  5  per  cent,  mercuric  acetate 
solution  is  added  just  sufficient  to  precipitate  the  tannins ;  the  mix- 
ture is  heated  to  500  C.  and  filtered,  the  insoluble  portion  being 
