Am  Jour.  Pharm.  1 
June,  1877.  j 
Collodion. 
•  I  have  had  the  most  success  with  the  following  old  formula  in  mak- 
ing pyroxylon  ;  in  fact  I  have  not  yet  had  a  failure  with  it :  Mix  in  a 
mortar,  of  the  proper  size,  7 \  ounces  of  granulated  nitrate  of  potassium 
and  6f  fluidounces  of  sulphuric  acid,  and  immediately  steep  in  it,  with 
the  aid  of  the  pestle,  180  grains  of  cotton,  freed  from  impurities.  Let 
stand  12  to  15  hours,  wash  the  product  thoroughly,  first  in  cold  and 
then  in  boiling  water,  and  dry  by  means  of  a  vapor-bath,  or,  if  it  is  to 
be  used  immediately,  displace  the  water  by  alcohol  and  express.  There 
is  another  version  of  the  same  formula,  saying:  Wash,  after  five  min- 
utes' immersion,  in  the  mixture  as  above,  first  in  cold  and  then  in  boil- 
ing water.  If  the  latter  is  done,  soluble  pyroxylon  will  not  be  obtained. 
When  the  washing  is  performed  in  cold  water  alone  the  product  will 
be  soluble  and  explosive,  but  if  it  is  completed  in  boiling  water  the  pro- 
duct will  lose  its  solubility  but  retain  its  explosiveness.  The  acid  used 
in  this  formula  may  vary  between  1*833  to  1*9  without  necessitating 
a  change  in  the  proportion. 
When  a  mixture  of  acid,  nitrate  of  potassium  and  cotton  has  stood 
12  to  15  hours  it  will  have  formed  into  a  solid  cake,  which  it  takes 
some  time  to  soften  sufficiently  that  the  pyroxylon  may  be  conveni- 
ently and  thoroughly  washed.  This  is  performed  first  in  cold  and  then 
in  boiling  water,  the  latter  in  this  instance  not  affecting  the  solubility 
of  the  product  in  the  least.  By  both  of  these  manipulations,  viz.,  12 
to  15  hours'  or  5  minutes'  immersion,  soluble  pyroxylon  is  obtained, 
providing  no  boiling  water  for  washing  is  used  after  the  latter. 
To  see  whether  the  temperature  of  the  mixture  had  any  appreciable 
influence  on  the  solubility  of  the  product,  instead  of  adding  the  cotton 
immediately  after  mixing  the  nitrate  of  potassium  and  sulphuric  acid, 
the  mixture  was  placed  aside  for  an  hour,  stirring  it  in  the  meantime 
three  or  four  times  to  prevent  caking.  Upon  mixture,  the  tempera- 
ture rose  to  I22°F.,  and  in  one  hour  it  had  fallen  to  780.  The  mix- 
ture now  had  a  viscid  consistence  something  like  granulated  honey,  and 
it  was  found  somewhat  difficult  to  incorporate  the  cotton.  After  24 
hours  the  product  was  thoroughly  washed  and  dried,  and  proved  to  be 
perfectly  soluble.  This  proves  tolerably  certain  that  the  temperature 
of  the  mixture  does  not  exert  any  influence  in  making  soluble  pyroxylon 
by  this  process. 
Whether  the  nitrate  of  potassium  formula  can  be  used  for  the  manu- 
