SULPHURETTED  HYDROGEN",  ETC.,  IN  TOBACCO  SMOKE.  7T 
precipitate  of  sulphuret  of  lead  was  dried  and  weighed,  after 
washing  with  alcohol. 
1.  Turkish  tobacco,  3-4  grms.  gave  7  milligrms.  of  sulphuret  of  lead. 
2.  "        "       3*7     "     u    7-5       u  u  " 
3.  German  cigars,    3        "     "    9         "  "  " 
Hence  the  presence  of  sulphuretted  hydrogen  in  tobacco  smoke 
is  unmistakably  proved.  The  presence  of  sulphuretted  hydrogen 
in  tobacco  smoke  may,  however,  be  proved  in  a  still  more  simple 
manner,  by  blowing  the  smoke  through  the  cigar  upon  a  piece 
of  paper  moistened  with  acetate  of  lead,  when  a  brown  color  is 
immediately  produced  on  the  spot  touched  by  the  smoke. 
The  well-known  reaction  of  sulphuretted  hydrogen  upon  nitro- 
prusside  of  sodium  is  exhibited  most  characteristically  when  a 
few  drops  of  a  solution  of  that  salt  mixed  with  ammonia  are  put 
into  a  test-tube  and  the  tobacco  smoke  is  introduced  by  a  tube, 
which  does  not  reach  quite  to  the  bottom  of  the  test-tube.  The 
walls  of  the  glass  moistened  with  the  solution  of  nitroprusside  of 
sodium,  by  shaking  acquire  a  deep  violet-red  color  by  the  action 
of  the  sulphuretted  hydrogen  of  the  tobacco  smoke.  The  above 
data  show  at  the  same  time  what  influence  the  incineration  of 
the  parts  of  plants  must  have  upon  the  accuracy  of  the  deter- 
mination of  the  sulphuric  acid  in  the  ashes. 
In  order  to  determine  directly  the  loss  of  sulphuric  acid  in  the 
ashes  caused  by  the  incineration,  the  amount  of  sulphuric  acid 
in  the  tobacco  ashes  produced  in  experiment  I  was  ascertained. 
From  this  it  appeared  that  of  100  parts  of  sulphuric  acid  in  the 
tobacco,  12-63  were  evolved  in  the  smoke  in  the  form  of  sul- 
phuretted hydrogen.  This  circumstance  is  consequently  of  im- 
portance in  the  determination  of  the  sulphuric  acid  in  incinerated 
parts  of  plants,  and  the  more  as  a  portion  of  the  sulphuretted 
hydrogen  also  escapes  observation  in  the  upper  part  of  the  smoke 
of  the  burning  tobacco. 
After  cyanogen  compounds  had  been  sought  in  vain,  even  in 
large  quantities  of  the  ashes  of  tobacco,  the  tobacco  smoke  it- 
self was  examined  for  cyanogen.  The  method  of  detecting 
hydrocyanic  acid  in  the  smoke  is  as  follows: — Tobacco  smoke  is 
passed  through  a  concentrated  solution  of  caustic  potash.  The 
solution  by  this  means  acquires  a  slight  brownish  color,  and 
when  a  turbidity  is  produced  by  dilution  with  water,  it  must  be 
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