ON  THE  ADULTERATION  OF  CARMINE. 
363 
are  necessary  ingredients  of  carmine,  and  are  never  contained 
in  that  pigment  in  a  sufficiently  large  quantity  for  them  to  be 
classed  as  adulterants,  I  did  not  think  it  important  to  take  any 
further  trouble  about  them.  The  filter,  retaining  alumina  and 
the  adulterating  agents  mentioned,  was  then  treated  with  ben- 
zole, which  has  the  property  of  dissolving  dragon's  blood  with 
formation  of  a  deep  red  solution.  Dragon's  blood  was  not,  how- 
ever, found  in  any  of  the  samples,  and  the  filter,  after  the  ben- 
zole had  been  removed  by  evaporation,  was  in  each  case  treated 
with  hydrochloric  acid ;  by  this  means  everything  was  dissolved 
off  except  vermilion,  which  could  be  washed,  dried,  and  weighed, 
the  loss  since  the  previous  weighing  giving,  of  course,  the  amount 
of  alumina  removed  by  the  hydrochloric  acid — red  lead,  and 
chrome-red  not  being  found  in  any  specimen  that  contained  ver- 
milion. If  chrome-red  were  present  in  the  sample,  the  filter, 
after  treating  with  hydrochloric  acid,  was  found  to  possess  its 
original  weight,  and,  therefore,  the  difference  between  that 
and  the  previous  weighing  gave  the  amount  of  chrome-red,  in- 
cluding what  little  alumina  might  be  present  with  it.  In  all 
cases  the  presence  of  the  substances  enumerated  was  confirmed 
by  qualitative  examination.  Red  lead  was  not  found  in  any  of 
the  specimens  examined,  and  of  course  alumina  was  not  classed 
as  an  adulterant.  It  was  not  perhaps  necessary  to  further  re- 
cognize the  vermilion,  as  scarcely  any  other  coloring  matter 
could  be  found  under  such  circumstances  ;  nevertheless,  the  test 
for  that  substance  given  some  years  ago  by  Bolley  (Annates  de 
Pharmacie,  75,  239,)  was  found  to  be  so  very  applicable  that  it 
was  always  used.  It  consists  in  adding  to  the  vermilion  a  drop 
or  two  of  solution  of  nitrate  of  silver  containing  considerable 
excess  of  ammonia;  a  black  color  is  quickly  produced  owing  to 
the  formation  of  sulphide  of  silver.  The  method  of  applying  the 
test  consisted  simply  in  placing  a  drop  of  it  on  the  filter  over 
which  was  spread  the  vermilion  from  the  decigramme  of  carmine, 
when  a  black  spot  was  instantly  produced. 
The  following  table  exhibits  at  a  glance  the  results  of  the 
examination  : — 
