ON  THE  PREPARATION  OF  CHLORIDE  OF  ZINC. 
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alcohol  to  make  a  pint  of  tincture.  Distil  off  three-fourths  of 
the  alcohol,  evaporate  the  residue  on  a  water-bath  to  a  thick, 
syrupy  consistence,  then  add  the  plaster  previously  liquefied, 
and  st ir  constantly,  until  it  is  properly  incorporated  with  the  soft 
resinous  extract,  and  cools.  The  resulting  aconite  plaster  has  a 
brown  color,  and  homogeneous  consistence,  and  weighs  about  four 
ounces  troy.  This  plaster  should  be  spread  in  a  thin  stratum  on 
skin  or  oiled  silk,  and  may  be  used  several  times  when  its  appli- 
cation has  not  been  too  long  continued  at  first. 
Dr.  Smith  has  employed  this  plaster  in  several  cases  of  neural- 
gia, especially  about  the  head,  and  has  obtained  from  it  the  well- 
marked  effects  of  aconite ;  in  some  instances  so  decided  as  to  re- 
quire the  removal  of  the  plaster  for  a  time.  He  has  also  used  it 
in  painful  tumors  of  the  breast  with  much  satisfaction. 
ON  THE  PREPARATION  OF  CHLORIDE  OF  ZINC. 
By  Benjamin  J.  Ckew. 
Having  been  recently  engaged  in  the  manufacture  of  chloride 
of  zinc  in  considerable  quantities,  and  not  being  satisfied  with 
the  product  when  prepared  strictly  in  accordance  with  the  for- 
mula of  our  Pharmacopoeia,  I  adopted  a  somewhat  different 
method,  and  meeting  with  entire  success,  I  have  thrown  toge- 
ther a  few  remarks  which  may  perhaps  be  useful  to  others  who 
have  experienced  the  same  difficulties.  In  the  officinal  formula 
the  quantity  of  hydrochloric  acid  requisite  to  dissolve  the  given 
quantity  of  metallic  zinc,  is  with  propriety  omitted  on  account 
of  the  variable  strength  of  commercial  acid.  Any  convenient 
quantity  of  zinc  may  be  used,  and  requires  between  three  and 
four  times  its  weight  of  acid  to  completely  dissolve  it ;  or  any 
convenient  bulk  of  acid  may  be  employed,  and  zinc  added  until 
effervescence  ceases  :  either  plan  may  be  used  without  difference 
of  result.  Having  obtained  a  neutral  solution,  it  is  filtered  or 
strained,  to  separate  the  black  sulphuret  of  zinc  which  has  been 
formed.  I  then  add  the  requisite  proportion  of  nitric  acid  to 
oxidize  any  iron  which  exists  in  the  commercial  muriatic  acid. 
The  solution,  upon  the  addition  of  the  acid,  assumes  a  dark 
brown  color,  which  is  dissipated  by  heat,  leaving  an  orange  hue. 
