368 
ALTHEA  PAPER  A  TEST  FOR  ACIDS,  ETC. 
leeted,  are  mostly  entire,  including  double  calyx  and  corolla, 
and  exhibit  only  the  dark  purple  variety  of  the  hollyhock,  and 
it  is  of  these  alone  I  speak.  By  leaving  them  for  a  few  minutes 
in  contact  with  water,  a  dark  bluish  purple  color  is  communica- 
ted, which  is  readily  imparted  to  the  common  white  filtering 
paper.  There  is  a  manifest  atmospheric  agency  at  work  in  the 
final  developement  of  the  color,  since  I  have  noticed  that  the 
slips  of  paper  after  immersion  in  the  colored  fluid  when  first 
brought  in  contact  with  the  air,  exhibit  a  decided  reddish  tint 
that  gradually  disappears,  and  gives  place  to  the  characteristic 
bluish  or  purplish  blue  tint,  which  then  becomes  permanent. 
This  very  permanency  of  the  color  gives  the  Althea  paper  an 
advantage  over  the  litmus  paper,  which  I  have  found  sometimes 
rendered  quite  useless  in  consequence  of  the  bleaching  agency 
of  even  diffused  light,  and  the  more  delicate  the  tint  of  the  pa- 
per, the  more  danger  of  such  destruction. 
I  have  had  the  Althea  paper  exposed  for  two  weeks  to  the 
direct  action  of  the  sunbeams  without  any  apparent  loss  of  color, 
and  am  inclined  to  believe  it  will  not  be  affected  by  any  length 
of  exposure  to  diffused  light.  Some  little  care  is  required  in 
preparing  the  paper  to  avoid  getting  too  deep  a  tint,  the  lighter 
shades  being  much  more  sensitive.  Two  drachms  of  the  entire 
dried  flowers  when  treated  with  sixteen  fluid  ounces  of  cold 
water,  are  sufficient  to  impart  the  proper  depth  of  color  for  a 
sensitive  test  paper. 
Two  or  three  ounces  of  water  should  be  first  poured  over  the 
flowers,  and  after  ten  minutes  infusion  the  rest  of  the  water 
added,  then  by  gently  pressing  the  flowers  at  intervals  with  a 
glass-rod,  and  stirring  the  liquid  for  five  minutes  longer,  it  will 
be  ready  for  use.  Slips  of  white  filtering  paper  once  immersed, 
and  dried  slowly  will  then  answer  as  a  substitute  for  the  litmus 
and  the  turmeric  paper  both,  as  the  Althea  paper  is  made  red 
by  acids,  and  green  or  rather  bluish-green  by  alkalies,  both 
changes  being  too  decided  to  be  overlooked  or  mistaken.  To 
approximate  the  comparative  value  of  the  new  test  color  I  insti- 
tuted a  comparative  trial  between  the  Althea  paper,  the  red 
litmus,  the  blue  litmus,  the  grey  litmus,  and  the  turmeric 
papers.  Using  for  this  purpose  at  one  time  the  same  alkaline, 
and  at  another  the  same  acid  liquid  for  all,  and  gradually  di- 
