GLEANINGS  FROM  THE  FRENCH  JOURNALS. 
21 
80  grammes  of  nitric  acid,  of  sp.  gr.  14,  The  porcelain  vessel 
is  set  in  another  of  boiling  water,  and  when  the  mixture  has 
attained  a  temperature  of  about  170°  F.,  the  cotton  well  carded 
and  of  the  best  quality,  is  added  in  quantity  sufficient  to  fill 
the  liquid  with  which  it  is  left  in  contact  five  minutes. 
The  liquid  is  then  rapidly  decanted,  the  pyroxylin  thrown 
into  a  vessel  of  water  and  washed  with  repeated  portions  of 
water,  and  then  macerated  for  a  night  in  water,  then  rinsed 
again,  pressed  and  dried. 
The  success  of  the  operation  depends  on  the  strength  of  the 
acids  as  indicated.  The  pyroxylin  obtained  is  very  short,  and 
in  the  form  of  coarse  powder ;  hence  the  washing  requires  care 
to  avoid  loss.  When  it  is  dry  it  is  put  in  a  bottle,  with  sufficient 
alcohol  to  cover  it.  Shake  the  bottle  occasionally  until  a  thick 
solution  is  obtained,  which  is  preserved  for  use. — Jour,  de 
JPharm. 
On  the  Silica  in  Commercial  Potash.  By  M.  Rieckher — 
The  purified  carbonate  of  potassa  retains,  as  is  well  known,  a 
certain  quantity  of  silica,  which  causes  its  solution  to  become 
cloudy  by  standing. 
Two  means  have  been  proposed  for  removing  the  silica :  the 
first  by  M.  Mohr,  which  consists  in  evaporating  the  solution 
till  the  carbonate  crystallizes,  when  the  silica  and  chloride  re- 
main in  the  mother-water. 
M.  Rieckher  proposes  to  evaporate  to  dryness  the  solution  of 
carbonate  of  potassa,  and  which  should  be  free  from  sulphate. 
After  cooling,  the  residue  is  moistened  with  carbonate  of  ammo- 
nia and  evaporated  again.  The  silica  passes  to  the  insoluble 
modification  by  aid  of  the  temperature  necessary  for  eva- 
poration.   By  again  dissolving  and  filtering,  the  carbonate 
is  obtained  free  from  silica  Jour,  de  Ohim.  Med.,  Nov., 
1863. 
New  Mat  Poison. — The  Journal  dy Agriculture  Pratique  re- 
commends artificial  carbonate  of  baryta  for  the  destruction  of 
rats.  This  tasteless  salt  can  be  mixed  with  different  aliments  ; 
it  does  not  become  poisonous  until  after  the  action  of  the  gas- 
tric juice  has  given  rise  to  soluble  salts  of  baryta. — Jour,  de 
Chim.  Med.,  Nov.,  1863. 
