258 
ON  THE  ADULTERATION  OF  TIN  FOIL. 
to  contain  a  large  amount  of  lead.  Believing  that  the  presence 
of  this  metal  in  such  considerable  quantity  in  the  foil  is  not  gen- 
erally known  and  recognized,  I  obtained  a  number  of  specimens 
of  commercial  foil  and  submitted  them  to  analysis.  Some  of 
these  were  kindly  supplied  to  me  by  Mr.  Haselden,  of  Conduit 
Street,  the  remainder  being  collected  by  myself.  They  consisted 
of — 1.  Ordinary  commercial  foil ;  2.  Embossed  foil ;  3.  Tinned 
paper ;  and  4.  Foil  lining  the  packets  of  Horniman's  tea ;  to- 
gether with  a  sample  of  <  Pure  Tin  Foil'  from  Mr.  Saddington's, 
and  some  of  Betts'  Patent  Capsules.  The  following  table  of  the 
results  of  the  analysis  in  the  several  cases  will  show  the  propor- 
tion of  lead  and  tin  present  in  the  different  samples.  The  pro- 
cesses employed  will  be  subsequently  described. 
12  3  Pure  Foil   Betts'  Capsules. 
Lead  86-93  76-57  88-665  34-375  84-56 
Tin    13-06       23-42       11-345       65-625  15-46 
99-99  99-99  100-000  100-000  100-02 
It  thus  appears  that  tin  foil  is  such  only  in  name,  though  the 
reason  of  this  large  admixture  of  lead  is  not  very  apparent,  be- 
cause the  so-called  pure  foil  noticed  above,  which  contains  a 
much  smaller  proportion  of  lead,  appears  to  be  in  every  respect 
better  suited  to  general  requirements,  being  at  once  thinner, 
lighter,  and  tougher.  The  only  cause  that  I  can  assign  is,  that 
the  alloy  may  be  more  easily  rolled  than  the  pure  metal.  I  may 
remark  that  the  sp.  gr.  of  the  alloy  is  less  than  would  be  indi- 
cated by  calculation  from  the  sp.  gr.  of  the  two  metals.  In 
Gmelin's  Work  a  table  is  given,  showing  the  actual  and  calcu- 
lated and  specific  gravities  of  these  two  metals  when  alloyed  in 
different  proportions. 
Not  long  since  there  was  a  great  deal  said  respecting  the 
packing  of  tea,  tobacco,  snuff,  etc.,  in  lead  foil,  as  in  several  in- 
stances accidents  had  occurred,  owing,  as  it  was  then  shown,  to 
the  formation  of  a  subcarbonate  of  lead,  which  was  disseminated 
through  the  contents  of  the  packet ;  and,  if  I  recollect  rightly, 
it  was  suggested  that  tin  foil  should  be  substituted  for  that  made 
from  lead.  If  it  is  true,  however,  that  tin  foil  is  itself  so  ex- 
tensively adulterated  with  lead,  it  is  obvious  that  no  advantage 
