550  Examination  of  Ericaceous  Plants.        {^^'-soV issT^' 
treated  with  a  solution  of  subacetate  of  lead  until  it  no  longer  pro- 
duced a  precipitate  ;  this  was  also  separated  by  a  filter  and  the  filtrate 
freed  from  the  lead  by  sulphuretted  hydrogen,  the  sulphide  of  lead 
separated  by  a  filter  and  the  excess  of  sulphuretted  hydrogen  expelled 
by  heating  the  filtrate.  The  filtrate  was  then  evaporated  to  a  syrupy 
consistence,  re-dissolved  in  Avater  and  treated  with  animal  charcoal, 
then  filtered  and  again  concentrated  and  while  hot  set  aside.  The 
solution,  on  standing,  deposited  crystals  of  arbutin  in  small  bunches 
of  needles  of  a  white  color. 
Concentrated  sulpliuric  or  hydrochloric  acid  added  to  the  crystals 
gradually  dissolved  them  without  change  of  color. 
With  nitric  acid  the  crystals  first  turned  black  and  then  slowly  dis- 
solved, the  acid  assuming  a  yellow  color  and  giving  off  fumes  of 
nitrous  acid. 
A  dilute  aqueous  solution  of  the  crystals  also  produced  the  charac- 
teristic l^lue  color  with  Jungmann's  phosphomolybdic  acid  and  ammo- 
nia test. 
This  test  will  also  produce  a  blue  color  with  solutions  of  morphia, 
aconitia,  atropia  and  berberina,  but  not  in  such  dilute  solutions  as  is 
the  case  with  arbutin,  of  which — according  to  Jungmann — 1  part  is 
distinctly  indicated  in  140,000  parts  of  Avater.  The  color  is  (in  each 
case)  dissipated  by  heat. 
With  a  view  to  ascertain  the  value  of  this  test  for  detecting  the 
presence  of  arbutin  in  plants  Avithout  isolating  it,  experiments  AA^ere 
made  Avith  the  infusions  of  belladonna,  aconite,  berberis,  digitalis,  senna, 
lobelia,  toxicodendron,  absinthium,  sabina  and  others.  The  infusions 
Avere  diluted  Avith  sufficient  AA^ater  to  make  them  perfectly  colorless, 
then  rendered  alkaline  Avith  ammonia ;  but  on  the  addition  of  phos- 
phomolybdic acid  they  did  not  produce  the  cliaracteristic  blue  color 
AAdiich  is  produced  AA^ith  infusions  of  the  ericaceous  plants  known  to 
contain  arbutin. 
Examination  of  the  Precipitates. 
1.  The  precipitate  obtained  on  adding  hydrated  oxide  of  lead  to 
the  infusion  of  the  leaves,  and  separating  by  a  filter,  Avas  Avell  Avashed 
and  dried,  then  suspended  in  Avater  and  decomposed  by  sulphuretted 
hydrogen  ;  the  sulphide  of  lead  AA^as  separated  by  a  filter  and  the 
excess  of  sulphuretted  hydrogen  expelled  by  heating  the  filtrate.  The 
filtrate  AA^as  then  concentrated  and  divided  into  two  parts. 
