ON  THE  PREPARATION  OF  COLLODION. 
215 
Experiment  4tt7i. — With  ice,  the  temperature  of  the  acids  was 
brought  to  32p  F.;  I  then  mixed  them  in  correct  proportions, 
and  found  the  temperature  to  rise  to  112°  F.  The  cotton  was 
now  added,  and  the  mixture  put  aside  for  ten  minutes  ;  it  was 
then  taken  out  and  thrown  into  a  quantity  of  water  and  well 
washed.  This  cotton  washes  well,  and  has  a  strong  nearly  per^ 
feet  fibre,  with  a  slightly  yellowish  appearance.  With  ether,  or 
alcohol  and  ether,  it  forms  a  gelatinous  mass,  which  is  partly 
dissolved  after  remaining  for  some  time.  It  increased  in  weighs 
about  40  per  cent.,  and  burns  quickly,  without  explosion. 
Experiment  5th. — I  made  a  nitro-sulphuric  acid  of  the  right 
strength,  and  the  temperature  rose  a  few  degrees  above  135°  F. 
After  the  acid  had  cooled  to  the  temperature  of  the  room,  I  added 
the  cotton,  and  treated  as  in  experiment  4th.  This  gained  50 
per  cent.,  and  was  slightly  explosive  and  partially  soluble.  The 
collodion  made  from  this  cotton,  will  nearly  always  have  minute 
fibres  suspended  in  it,  which  settle  only  with  much  difficulty. 
The  foregoing  experiments  are  sufficiently  conclusive  to  evince 
the  necessity — first,  to  have  the  nitro-sulphuric  acid  of  the  proper 
strength  ;  secondly,  that  the  acids,  before  mixing,  should  have 
the  temperature  of  at  least  65°  F.;  and  thirdly,  that  the  cotton 
should  be  added  directly  after  the  acids  are  mixed,  or  when  the 
thermometer  indicates  about  130°  F. 
By  strictly  observing  these  rules  all  the  causes  of  disappoint- 
ment are  obviated,  and  the  result  will  be  a  perfectly  soluble  cotton. 
It  now  remains  to  give  a  formula  for  its  preparation,  and,  in 
doing  so,  I  give  one  that  many  experiments  have  proved  to  be 
successful.    It  is  as  follows  : 
Fuming  nitric  acid  (sp.  gr.  145),  7  of  each,  one 
Sulphuric  acid  (commercial),        $  fluid  ounce. 
Water,       ....        one  fluid  drachm, 
Cotton  (carded),  .        .         sixty  grains, 
Ether  (commercial),      .        .         twelve  fl.  ounces. 
or : 
•  Fuming  nitric  acid  (sp.  gr.  142),  )  of  each,  one 
Sulphuric  acid  (commercial),       j  fluid  ounce. 
Cotton  (carded),        .        .       .    sixty  grains, 
Ether  (commercial),  .       .       .    twelve  fl.  ounces. 
