Am  oc°tu,r'i7h7arm'}  Liquor  Potassii  Arsenitis.  503 
ounce  of  water  instead  of  twelve  fluidounces,  as  a  more  concentrated 
solution  of  the  potassium  salt  is  formed  and  hastens  the  action  during 
the  heating  process.  The  substitution  of  the  bicarbonate  for  the  car- 
bonate is  perhaps  of  no  great  importance,  except  as  lessening  the 
alkalinity  of  the  finished  product,  as  above  noticed,  and  furnishing  a 
slightly  purer  salt,  practically  of  no  advantage  to  the  preparation. 
There  still  seems  room  for  improvement,  and  the  following  process 
is  offered  as  such.  Its  merit  consists  in  easy  and  rapid  execution  and 
simplicity  of  apparatus  required,  also  the  large  amount  that  may  be 
produced  with  vessels  of  small  capacity. 
Take  of  Arsenious  acid  in  small  pieces,  .       sixty-four  grains. 
Potassa  (hydrate,  fused),  .  thirty-six  grains. 
Compound  spirit  of  lavender,  .       half  a  fluidounce. 
Distilled  water,  a  sufficient  quantity. 
Rub  the  arsenious  acid  to  a  fine  powder  in  a  small  glass  or  porcelain 
mortar,  add  the  potassa  and  one  fluidrachm  of  distilled  water  and  tritur- 
ate thoroughly  together  until  a  slightly  creamy  solution  is  formed. 
Then  carefully  pour  the  yet  imperfect  solution  into  a  test-tube  or  small 
evaporating  dish  and  apply  heat  until  perfect  solution  is  effected.  Pour 
the  hot  solution  carefully  back  into  the  mortar,  and  stir  it  with  the 
pestle  to  take  up  the  portion  of  syrupy  liquid  that  adhered  to  their  sur- 
faces in  the  act  of  first  emptying  the  mortar.  Should  the  hot  solution 
not  effect  complete  solution  of  the  remainder  in  the  mortar,  return  the 
mixed  liquids  into  the  test-tube,  apply  heat,  and  repeat  the  rinsing  of 
mortar  and  pestle  as  before.  Proceed  thus  till  all  the  arsenious  acid  is 
completely  dissolved,  then  add  twelve  fluidounces  of  distilled  water, 
rinsing  mortar  and  pestle  and  test-tube  with  the  same,  and  mix  the  dif- 
ferent portions  in  a  suitable  graduated  measure.  Then  add  the  com- 
pound spirit  of  lavender,  and  finally  sufficient  distilled  water  to  make 
the  whole  product  measure  one  pint ;  filter. 
By  this  method  I  am  sure  that  the  whole  may  be  finished  in  ten 
minutes  or  less,  except  filtering,  which  is  advisable  in  order  to  remove 
a  very  little  silica  that  is  nearly  always  a  constituent  of  hydrate  or  caustic 
potassa.  The  gain  in  time  and  facility  of  making  the  solution  arises 
principally  from  two  sources  ;  in  the  first  place  a  most  potent  form  of 
the  alkali  is  substituted  for  a  weak  one,  and,  secondly,  by  the  use  of  a 
very  little  water  a  decidedly  concentrated  solution  of  the  potassa  is 
brought  in  contact  with  the  arsenious  acid.     But  there  are  two  other, 
