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METHOD  OF  PREPAKING  LACTATE  OP  ZINC. 
to  constant  wear.  Paper,  after  having  been  printed  either  from 
the  surface  or  in  intaglio,  is  still  capable  of  conversion  by  Mr. 
Gaine's  method  ;  no  part  of  the  printed  matter  being  obliterated 
by  the  process.  Parchment-paper  also  promises  to  be  of  value 
for  photographic  purposes,*  and  also  for  artistic  uses,  in  conse- 
quence of  the  manner  in  which  it  bears  both  oil  and  water-color. 
It  isabout  to  be  introduced  into  commerce  by  Messrs.  Thomas 
de  la  Rue  and  Co. — London,  Pharm.  Jour.  June  1,  1857. 
METHOD  OF  PREPARING  LACTATE  OF  ZINC.   FORMULiE  FOR 
ITS  EMPLOYMENT. 
By  Dr.  Herpin. 
Lactate  of  zinc  has  not  hitherto  been  used  in  medicine.  Dr. 
Herpin  has  recently  shown  the  advantages  which  may  be  derived 
from  its  use  in  the  treatment  of  epilepsy ;  we  shall  extract  from 
his  memoir  the  facts  relative  to  the  preparation  and  properties 
of  the  salt. 
Lactate  of  zinc  may  be  obtained,  1st,  by  the  saturation  of 
lactic  acid  ;  2nd,  by  double  decomposition. 
First  Process. — Lactic  acid  is  put  in  contact  with  pulverised 
zinc.  The  metal  dissolves,  and  lactate  of  zinc  is  formed,  with  a 
disengagement  of  hydrogen.  Lactic  acid  may  likewise  be  satu- 
rated by  oxide  of  zinc,  or  better  still  by  the  carbonate  of  this 
base,  both  being  freshly  precipitated  and  carefully  washed.  In 
the  latter  case,  when  once  the  disengagement  of  carbonic  acid 
ceases,  so  as  to  saturate  every  trace  of  acid,  it  is  boiled  and 
filtered ;  on  cooling,  it  deposits  crystals  of  lactate  of  zinc. 
They  only  require  one  or  two  crystallisations  to  obtain  a  per- 
fectly pure  product. 
Second  Process. — The  preparation  of  lactate  of  zinc  by  double 
decomposition  necessitates  two  distinct  operations ;  the  first  con- 
sists in  transforming  lactate  of  lime  into  lactate  of  potassa ;  the 
second  in  putting  together  lactate  of  potassa  and  acetate  of  zinc 
to  obtain  lactate  of  zinc. 
When  a  solution  of  lactate  of  lime  is  precipitated  by  carbonate 
of  potassa,  carbonate  of  lime  is  deposited  and  the  liquor  contains 
*  Photographs  on  this  paper  were  exhibited. 
