CONTRIBUTIONS  TO  THE  THEORY  OF  DYEING. 
359 
the  fact  that  the  precipitates  weighed  in  this  manner  are  definite 
compounds,  the  specific  gravity  of  which  is  well  ascertained. 
The  principle  I  have  exemplified  above  may  not  be  novel;  but 
as  I  have  never  met  with  it,  chemists,  a3  well  as  manufacturers 
(especially  of  colors),  will  probably  also  find  it  of  interest,  and 
certainly  highly  practicable  and  easy  of  execution. — -Am.  Jour. 
Science  and  Arts,  March,  1860. 
CRITICAL    AND   EXPERIMENTAL   CONTRIBUTIONS  TO  THE 
THEORY  OF  DYEING. 
Under  this  title  a  somewhat  extended  treatise,  by  Prof.  Bol- 
LEY  of  Zurich,  has  appeared  in  the  L.  E.  and  D.  Philosophical 
Mag.  [4]  xviii.  481,  Supplement  to  Dec.  1859. 
Two  questions  have  long  been  agitated  among  chemists  inter- 
ested in  the  theory  of  dyeing.  In  what  part  of  the  colored 
fibre  is  the  coloring  matter  situated  ?  Does  it  merely  adhere  to 
the  surface,  or  does  it  penetrate  the  entire  substance  of  the  cell- 
walls  of  such  fibres  as  cotton  and  flax  ?  Or  lastly,  in  the  case 
of  such  fibres  is  it  stored  up  in  the  interior  of  the  cells?  (2.) 
What  is  the  nature  of  the  union  between  the  dye  and  the  fibre  ? 
Is  it  a  chemical  combination,  or  is  it  due  to  mere  surface  attrac- 
tion ?  After  comparing  the  various  theories  which  have  been 
advanced  during  the  last  century  and  discussing  the  merits  of 
each,  the  author  records  the  results  of  his  own  experiments,  from 
which  it  appears  that  wool  and  silk  in  all  cases  where  they  have 
not  been  dyed  with  colors  in  a  mere  state  of  suspension*  seem  to 
be  impregnated  with  the  dye  throughout  their  entire  mass  ;  while 
in  the  case  of  cotton,  by  far  the  larger  portion  of  the  coloring 
matter  adheres  to  the  surface  of  the  fibre,  the  penetration  of  the 
cell-walls  by  the  dye  being  either  very  slight  or  altogether 
wanting. 
That  the  theory  of  W.  Crum  (L,  E.  and  D.  Phil.  Mag.,  April 
1844, — compare  this  Journal  [2],  xxviii.  125), — in  accordance 
with  which  the  tubular  form  of  the  cotton  fibres  is  an  essential 
condition  to  their  taking  a  dye,  is  unfounded,  appears  from  the 
*  In  which  case  the  coloring  matter  only  adheres  as  a  crust  to  the  sur- 
face of  the  fibre. 
