AMj£™;S?2RM*}         Litmus  Paper  as  a  Reagent.  9 
Having  mounted  a  Bohemian  glass-funnel  and  a  cylindrical  glass- 
percolator,  each  with  a  sufficient  amount  of  material  to  obtain  four 
pints  of  tinct.  gentianse  co.,  my  results  were  as  follows  : 
From  the  glass    From  cylindrical  glass 
funnel.  percolator. 
The  first  pint  of  diluted  alcohol  coming 
through,  increased  in  weight  ^i,  ^iij,  gr.  iv.     gi,  Bi. 
The  second  pint,  lj,  Bj.  3vi.  gr.  xxiij. 
The  third  pint,  3v,  gr.  xiij.  ^iij. 
The  fourth  pint,  3U,  9j-  3h  gr-  iv- 
In  various  other  experiments  I  have  always  been  able  to  obtain  far 
better  results,  and  to  exhaust  the  material  more  thoroughly  by  em- 
ploying the  glass-funnel. 
LITMUS  PAPER  AS  A  REAGENT. 
By  Charles  Bullock. 
In  using  litmus  paper  as  a  reagent  to  detect  the  presence  of  acids 
and  alkalies,  the  suggestion  sometimes  occurs  "  what  amount  of  acids 
or  alkalies  is  necessary  to  give  a  distinct  change  of  color  to  the  test 
paper  ?" 
The  result  of  a  few  experiments  to  determine  approximately  the 
above  question,  may  be  of  interest  to  the  readers  of  the  Journal. 
Blue  litmus  paper  should  be  distinctly  blue,  but  not  a  deep  shade 
in  color.  The  directions  given  by  Fresenius  in  his  Qualitative  Analy- 
sis will  afford  a  sensitive  paper ;  when  carefully  made  it  affords  the 
reactions  with  one  drop  of  acetic  acid  No.  8  (30  per  cent,  acid)  in  the 
following  amounts  of  water  : 
In  four  ounces  of  water  it  turns  red  immediately  ;  in  six  ounces, 
completely  red  in  one-half  minute  ;  in  ten  ounces,  changes  on  the 
edges  in  one-fourth  minute  and  is  completely  reddened  in  one  min- 
ute :  in  13  ounces  it  is  completely  red  in  a  minute  and  a  half,  and  re- 
mains red  when  dry.  In  16  ounces  of  water  the  limit  of  distinct  re- 
action is  found. 
Reddened  litmus  paper.  Reddened  litmus  solution  should  have  a  pur- 
ple red  color,  and  the  paper,  when  dry,  a  distinct  red  color  free  from 
blue. 
With  one  grain  anhydrous  carbonate  of  soda  in  32  ounces  of  water, 
the  paper  turns  blue  in  one  minute  ;  in  56  ounces  of  water,  in  three 
