344 
ON  ARSENIC  IN  PAPER-HANGINGS. 
of  which  the  walls  were  covered  with  paper  hangings,  exhibiting 
a  large  pattern  of  a  light  green  color.  The  surface  of  the  paper 
was  not  glazed,  and  the  colored  portions  were  found  to  have  on 
their  surface  about  two-tenths  of  a  grain  of  arsenic  per  square 
inch.  In  the  first  experiment  the  room  was  kept  thoroughly 
closed  for  about  thirty  six  hours ;  a  portion  of  its  atmospheric 
contents  were  then  drawn,  by  an  aspirator,  first  through  a  solu- 
tion of  nitrate  of  silver,  and  then  through  a  tube  containing 
asbestos  moistened  with  ammonio-nitrate  of  silver.  In  the 
second  experiment,  air  was  passed  through  these  tests  for  a 
longer  period  than  in  the  first  (about  five  hours),  and  three  gas- 
lights had  previously  been  kept  burning  in  the  well-closed  room 
for  several  hours.  Not  a  trace  of  arsenic  was  detected  by  a 
careful  examination  of  the  tests  at  the  close  of  these  experiments. 
3rd  Experiment. — A  large  glass  tube  (3  feet  3  inches  in 
length,  and  2  inches  in  diameter)  was  next  filled  with  slips  of 
arsenical  paper-hangings,  placed  in  a  small  room,  in  a  position 
where  it  could  be  raised  to  a  temperature  of  about  90°  F.,  and 
connected  with  a  similar  apparatus  to  that  employed  in  the 
former  experiments,  containing  solutions  of  nitrate  and  ammonio- 
nitrate  of  silver.  Air  was  then  drawn  through  the  apparatus 
uninterruptedly  for  one  week  (by  means  of  a  J ohnston' s  Aspira- 
tor},  three  gaslights  being  kept  burning  in  the  closed  room,  at 
intervals,  for  several  hours.  The  air  passed  through  the  ap- 
paratus at  the  rate  of  one  cubic  foot  in  two  hours. 
4th  Experiment.— Air  was  passed  through  the  apparatus,  as 
before,  for  twenty-four  hours  ;  the  tube  containing  the  paper 
was  kept  warm,  and  the  air  was  made  to  pass  through  a  strong 
solution  of  sulphurous  acid  before  it  reached  the  tube. 
5th  Experiment. — The  end  of  the  tube  at  which  the  air  en- 
tered was  connected  with  a  large  funnel  suspended  immediately 
over  a  burning  gas-jet ;  hot  air,  mingled  with  the  products  of 
the  combustion  of  gas,  was  thus  made  to  pass  over  the  paper  for 
three  days. 
6th  Experiment. — The  fifth  experiment  was  repeated,  the  air 
being  passed  uninterruptedly  for  four  days. 
7th  Experiment. — Hot  air  was  passed  through  the  tube,  as 
in  the  fifth  and  sixth  experiments,  for  nine  days,  the  colored 
surface  of  the  arsenical  paper  having  first  been  thoroughly 
roughened  by  friction,  so  as  to  promote  the  mechanical  detach- 
