3°2 
Collodion. 
{Am.  Jour.  Pharm. 
June,  1877. 
acid  of  sp.  gr.  1*5  makes  a  pyroxylon  which  is  not  entirely  soluble  in 
ether;  but  nitric  acid  of  sp.  gr.  1*42  answers  much  better."  This  is 
from  "  Pereira's  Materia  Medica,"  etc. 
According  to  the  "  Pharmacopoeia,"  a  half  troyounce  of  cotton, 
freed  from  impurities,  is  thoroughly  imbued  in  a  mixture  of  three  and 
a  half  troyounces  of  nitric  acid  and  four  troyounces  of  sulphuric  acid 
of  officinal  strength  for  fifteen  hours,  after  the  temperature  of  the  mix- 
ture has  fallen  to  900.  The  product  is  then  washed,  first  in  cold  water, 
until  the  washings  cease  to  have  an  acid  taste,  and  then  in  boiling 
water,  then  drained  on  filtering  paper  and  dried  by  means  of  a  water 
bath.  If  acids  of  the  officinal  strength  can  not  be  easily  obtained, 
for  the  same  quantity  of  cotton  a  mixture  of  four  troyounces  of  nitric 
acid,  sp.  gr.  1*382  to  1*390,  and  of  sulphuric  acid,  sp.  gr.  1*833  ten 
troyounces  is  used,  and  proceeded  as  before.  I  have  tried  both  of  these 
formulae  and  have  had  tolerably  good  success  with  the  second  when 
the  directions  were  scrupulously  followed. 
Hager,  in  his  commentaries  to  the  "  Pharmacopoeia  Germanica," 
gives  a  table  of  mixtures  for  the  preparation  of  pyroxylon,  which  I 
give  below.  It  shows  the  proportion  and  the  sp.  gr.  of  the  acids  in 
each  mixture,  and  the  number  of  hours  necessary  to  complete  the 
chemical  change  in  the  cotton  : 
Nitric  Acid.  Sulphuric  Acid. 
Spec.gr.  x'833-1'840. 
Parts. 
Spec.  gr. 
Parts. 
Hours. 
1 1 
1*460 
1 1 
5 
12 
1*450 
12 
6 
12* 
1-440 
13 
7 
13 
1-430 
14* 
8 
14 
1*420 
l6 
9 
15 
1*410 
17 
10 
16 
1*400 
i8| 
12 
17 
1*390 
20 
1.5 
18 
1*380 
22 
20 
Comparing  the  second  formula  of  the  "  Pharmacopoeia "  with  the 
one  that  ought  about  to  correspond  with  it  in  this  table,  a  conspicuous 
difference  is  noticed.  The  former  uses  four  parts  nitric  acid,  sp.  gr. 
1*390,  to  ten  parts  sulphuric  acid,  sp.  gr.  1*833,  whereas,  the  latter  uses 
seventeen  parts  nitric  acid,  sp.  gr.  1*390,  to  twenty  sulphuric  acid,  sp.  gr. 
1*833-1*840.  Whether  this  mixture  of  Hager  makes  soluble  pyroxy- 
lon I  cannot  say.  I  have  used  mixtures  approaching  it  in  composition, 
but  never  with  success. 
