44 
EXTRACTION  OP  THALLIUM. 
by  Mr.  Taylor  with  the  most  scrupulous  care  in  the  spectroscope, 
but  have  been  unable  to  see  the  faintest  trace  of  the  green  line. 
Had  thallium  been  present  it  would  scarcely  have  escaped  the 
keen  observation  of  Berzelius — that  most  acute  and  persevering 
of  modern  chemists. 
Amongst  those  manufacturing  firms  to  whom  I  am  indebted 
for  flue  dust,  my  thanks  are  especially  due  to  the  Walker  Alkali 
Company  and  Messrs.  Allhusen  and  Sons,  of  this  town,  Mr. 
Spence  and  Messrs.  Roberts,  Dale,  and  Company,  of  Manches- 
ter, Messrs.  Chance  Brothers,  and  Adkins  and  Company,  of 
Birmingham,  the  Metropolitan  Alum  Company,  of  Bow,  and 
Messrs.  Wilson  and  Son,  Glasgow.  From  each  of  these  firms 
I  have  received  every  assistance  which  I  could  desire,  in  speci- 
mens from  different  parts  of  the  flues,  and  their  entire  stock  of 
thalliferous  flue  dust,  varying  in  quantity  from  one  or  two  up  to 
thirty  cwts.  Were  I  to  mention  those  who  have  kindly  forward- 
ed me  specimens — unfortunately  containing  no  thallium— -I 
should  have  to  give  a  catalogue  of  half  the  chemical  works  in 
the  kingdom.  My  thanks  are  particularly  due  to  J.  Lowthian 
Bell,  Esq.,  Mayor  of  Newcastle,  for  the  handsome  present  of 
an  ingot  of  thallium,  weighing  half  a  pound,  prepared  at  his 
aluminium  works  at  Washington. 
The  flue  dust  upon  which  we  have  as  yet  operated  amounts  to 
about  five  tons,  the  whole  of  which  has  been  treated  by  the 
method  I  am  about  to  describe.  Some  of  the  gentlemen  I  see 
around  me  who  are  in  the  daily  habit  of  dealing  with  much  larger 
quantities  of  materials,  may  perhaps  smile  at  the  mention  of  dif- 
ficulties of  manipulating  such  an  amount,  and  yet  even  in  the 
well-appointed  laboratory  of  Messrs.  Hopkin  and  Williams,  and 
with  the  valuable  personal  superintendence  of  these  gentlemen, 
the  difficulties  have  been  very  serious.  In  the  first  place,  the 
whole  of  the  material  had  to  be  boiled  in  water  and  then  filtered. 
As  a  matter  of  course  the  filtrate  is  extremely  acid,  and  notwith- 
standing the  most  careful  watching,  the  filters  would  occasionally 
break,  and  a  considerable  loss  of  material  ensue.  Then  again, 
when  the  liquor  is  left  to  deposit,  so  that  the  thallium  solution 
may  be  decanted,  the  residue  occasionally  sets  into  a  hard  com- 
pact mass,  which  expands  in  cooling,  and  splits  the  vessel  in 
which  it  is  placed.  In  this  way  we  had  the  misfortune  to  lose 
m  any  pounds  of  metal ;  three  twenty-gallon  pans  have  been 
