362 
ON  THE  ADULTERATION  OF  CARMINE. 
casionally  with  albumen,  should  constitute  the  manufactured 
carmine  of  commerce. 
The  great  value  of  carmine  as  a  pigment  depends  upon  the 
facts  that  it  is  richer,  more  transparent,  and  a  smaller  quantity 
goes  further  than  any  other  color  of  similar  hue.  It  is  largely 
used  by  artists,  especially  in  miniature  painting,  also  by  artificial 
flower  makers,  perfumers,  confectioners,  red-ink  manufacturers, 
and — when  mixed  with  powdered  French  chalk,  starch,  &c. — 
as  a  face-paint,  under  the  name  of  rouge. 
That  for  all  these  purposes  carmine  is  adulterated  is  probably 
well  known ;  indeed,  its  great  expense  would  at  once  point  it 
out  as  an  article  peculiarly  liable  to  sophistication.  Moreover, 
mostiof  the  works  on  Applied  Chemistry  indicate  that  it  is  likely 
to  contain  vermilion,  and  that  a  test  of  its  purity  is  its  being 
completely  soluble  in  solution  of  ammonia,  in  which,  of  course, 
vermilion  is  insoluble.  Practised  artists  well  know  this,  and,  as 
I  am  informed  by  Mr.  Ince,  often  will  not  purchase  carmine  un- 
less the  test  is  performed  in  their  presence. 
The  extent,  however,  to  which  this  adulteration  is  carried  is, 
I  think,  not  generally  suspected  ;  nor  is  it  commonly  known 
that  chrome-red  (dichromate  of  lead)  is  often  used  as  an  adulter- 
ant in  the  place  of  the  more  expensive  vermilion.  For  these 
reasons  it  has  occurred  to  me  that  a  statement  of  the  results  of 
a  quantitative  examination  of  fifteen  different  samples  of  carmine 
would  not  be  without  some  practical  interest  to  the  members  of 
the  Society. 
Starting  with  the  assumption  that  carmine  might  be  contamin- 
ated with  vermilion,  chrome-red,  red  lead,  dragon's  blood,  and 
possibly  some  other  matters  that  would  be  sure  to  show  them- 
selves in  the  course  of  analysis,  the  following  was  the  method  of 
examination  finally  adopted.  A  decigramme  (one  and  a  half 
grains)  was  digested  for  a  short  time  in  about  half  an  ounce  of 
weak  solution  of  ammonia,  the  mixture  thrown  on  to  a  weighed 
filter,  and  the  filter  washed  with  warm  distilled  water,  dried  at 
212°  F.,  and  weighed ;  the  loss  of  weight  suffered  by  the  deci- 
gramme would  then  indicate  what  per-centage  of  the  carmine 
had  been  dissolved  by  the  ammonia.  In  addition  to  carminic 
acid,  the  ammoniacal  solution  would,  I  suppose,  contain  any  oxide 
of  tin  or  albumen  that  might  have  been  present ;  but,  as  these 
