214 
ON  THE  PREPARATION  OP  COLLODION. 
short,  rotten  fibre.  When  dry,  it  was  found  to  have  lost  14  grains 
in  the  operation.  This  cotton  was  perfectly  soluble,  making  a 
limpid  collodion  when  dissolved  in  ether,  or  alcohol  and  ether, 
and  leaving  a  transparent  film  when  dropped  upon  glass.  It  is 
not  explosive,  but  burns  quietly.  This  formula,  though  one  of 
much  loss  to  the  manufacturer,  will  sometimes  make  a  soluble 
cotton,  but  it  does  not  thicken,  or  give  the  collodion  a  mucila- 
ginous appearance,  to  the  desired  extent.  There  is  danger  when 
the  cotton  is  added,  of  its  taking  fire  and  being  entirely  con- 
sumed, unless  carefully  watched. 
Experiment  3rd. — A  mixture  was  made  with  three'  drachms 
of  nitric  acid  and  five  of  sulphuric,  which  increased  from  74°  to 
120°  F.;  80  grains  of  cotton,  treated  as  in  the  former  experi- 
ments, was  found  to  have  gained  20  grains,  entirely  insoluble  at 
first,  but  after  remaining  in  a  mixture  of  alcohol  and  ether  a  few 
days,  it  changed  into  a  partially  gelatinous  mass  .This  cotton  is 
very  explosive,  leaving  no  residue  ;  harsh  to  the  touch,  and  to 
all  appearances  had  undergone  no  change.  The  above  experi- 
ments are  quite  sufficient  to  show  the  most  prominent  varieties 
which  result  during  the  temperature  of  summer. 
In  my  1st  experiment,  the  nitro-sulphuric  acid  was  rather  too 
strong,  thus  rendering  the  cotton  slightly  explosive  and  only 
partially  soluble. 
In  my  2nd,  the  acid  was  much  too  weak,  causing  the  cotton  to 
be  partly  dissolved  in  it,  and  the  fibre  to  be  short  and  matted, 
and  not  difficult  to  pulverize  when  dry. 
My  3rd  shows  that  the  acid  was  entirely  too  strong,  making 
the  cotton  insoluble  and  very  explosive,  gaining  much  in  weight, 
with  a  perfect  fibre.  Frequent  experiments  have  shown  that  the 
acids  may  be  of  the  right  strength,  and  mixed  in  correct  pro- 
portions, but  unless  the  temperature  of  them  be  of  such  a  degree 
as  to  cause  the  nitro-sulphuric  acid  to  rise  to  130°  or  135°  F., 
the  cotton  will  not  be  perfectly  soluble.  The  rise  of  the  tempera- 
ture to  the  above  degree,  when  the  acids  are  mixed,  seems  to 
cause  a  change  necessary  to  effect  a  soluble  cotton.  Before  going 
further,  it  will  be  necessary  to  undertake  a  few  experiments  to 
show  if  it  is  absolutely  required,  in  effecting  a  soluble  cotton, 
for  the  temperature  of  the  acids,  when  mixed,  to  rise  to  180° 
or  135°  F.,  and  also  if  it  is  necessary  to  add  the  cotton  during 
this  high  temperature.,  or  after  it  has  cooled. 
