Am'jJi?,r,i£17.ar,n'}    Preparation  of  Surgical  Dressings.  357 
ation  of  iodine.  Ether  prepared  from  sulphuric  acid  and  alcohol  lib- 
erates iodine  from  strong  solutions  of  potassium  iodide,  and  very  slowly 
from  dilute  solutions,  the  reaction  being  accelerated  by  the  presence  of 
acid.  The  reaction  is  not  due  to  ozone,  for  on  agitating  the  ether  with 
mercury  or  silver  the  nitrate  had  the  same  behavior  before.  On 
warming  the  ether  with  solution  of  sodium  carbonate,  neither  the 
escaping  gas  nor  the  remaining  ether  had  any  effect  upon  potassium 
iodide.  The  presence  of  hydrogen  peroxide,  thus  indicated,  was  shown 
by  shaking  the  ether  with  a  very  dilute  solution  of  potassium  chro- 
mate  acidulated  with  sulphuric  acid,  when  the  ether  separated  of  a 
deep  blue  color,  due  to  perchromic  acid.  Some  commercial  ethers, 
particularly  if  made  from  methylated  spirit,  contain  an  impurity  which 
forms  H202  after  a  short  time,  and  this  may  then  be  detected  by  the 
perchromate  test.  The  quantity  of  H202  amounted  to  only  *04  per 
cent,  determined  from. the  iodine  liberated.  The  impurity  may  be  re- 
moved by  treating  the  ether  with  excess  of  lime  and  washing  the  dis- 
tillate with  alkaline  water. 
PREPARATION  OF  SURGICAL  DRESSINGS. 
The  French  military  authorities  have  caused  steps  to  be  taken  for 
purifying  charpie  before  rendering  it  antiseptic,  and  the  mode  of  im- 
buing it  with  the  several  kinds  of  antiseptic  preparations  are  laid  down 
with  great  precision.  To  purify  the  charpie,  four  litres  of  boiling 
water  are  to  be  poured  on  each  kilogram ;  this  is  to  be  allowed  to 
cool,  and  the  charpie  is  then  to  be  removed  and  washed  freely  in  fresh 
water  until  the  water  passes  off  perfectly  clear.  The  charpie,  after  the 
water  has  been  pressed  out,  is  next  to  be  soaked  for  three-quarters  of 
an  hour  in  six  litres  of  a  solution,  1  in  30,  of  chloride  of  lime,  and 
again  washed  in  water  until  all  odor  of  the  chloride  has  disappeared. 
The  charpie  is  then  put  into  six  litres  of  dilute  hydrochloric  acid,  1  in 
30,  and,  half-an-hour  afterwards,  is  withdrawn  and  washed,  until  it 
does  not  redden  litmus  paper.  It  is  now  pressed,  dried,  and  rubbed 
until  it  is  sufficiently  supple.  The  following  are  the  preparations  em- 
ployed for  rendering  the  purified  charpie  antiseptic. 
For  the  mercurial  charpie  (charpie  bichloruree)  1  gram  of  the  bi- 
chloride of  mercury  is  dissolved  in  100  grams  of  alcohol;  and  this 
solution,  together  with  10  grams  of  glycerin  and  10  grams  of  Senegal 
gum,  is  added  to  2J  kilograms  of  distilled  water.    Into  this  solution 
