Am.  Jour.  Pharm. 
June,  19 18. 
Antiseptics. 
441 
By  adding  boric  acid  to  chlorinated  lime  in  the  proportions  above 
stated  we  have  produced  a  solution  containing  calcium  biborate, 
an  acid  salt  of  extremely  low  hydrogen  ion  concentration ;  on  mix- 
ing such  a  solution  with  one  containing  hydrochloric  acid  the  acid- 
ity is  reduced  as  the  free  H  ions  are  taken  up  by  the  solution, 
therefore  cannot  rise  above  the  dissociation  constant  for  boric  acid, 
which  is  very  low. 
By  this  adjustment  various  advantages  have  been  secured :  the 
alkalinity  of  the  chloride  of  lime  has  been  reduced,  the  full  effect  of 
the  free  hypochlorous  acid  has  been  secured,  and  the  solution  cannot 
become  unduly  acid.  In  virtue  of  this  balance  it  follows  that  the 
solution  can  be  applied  freely  to  the  tissues  of  the  body,  and  that  a 
considerable  quantity  can  be  injected  into  the  circulating  blood  with- 
out harmful  effect. 
The  high  germicidal  value  of  pure  hypochlorous  acid  solutions 
was  demonstrated  in  1903  by  Andrews  and  Orton.4  In  test-tube  ex- 
periments they  found  that  very  weak  solutions  of  hypochlorous 
acid,  1  part  in  100,000,  would  kill  pathogenic  organisms  in  one 
minute  but  when  applied  to  solutions  containing  organic  matter  as 
well  as  bacteria  they  found  the  hypochlorous  acid  so  rapidly  de- 
stroyed that  they  did  not  evolve  any  method  of  applying  the  solution 
as  a  practical  antiseptic. 
Putting  all  the  above  observations  together  we  fixed  on  the  fol- 
lowing as  safe  antiseptics : 
The  powder,  equal  weights  of  chloride  of  lime  and  boric  acid. 
The  solution,  prepared  by  shaking  up  25  Gm.  of  the  above  mixture 
in  one  liter  of  water  and  filtering  off  the  sediment;  this  solution  con- 
tains about  0.26  per  cent,  hypochlorous  acid.  The  powder  we 
named  Eupad  and  the  solution  Eusol — words  derived  from  the 
initial  letters  of  Edinburgh  University  Pathology  Department. 
A  simple  and  convenient  method  of  preparing  small  quantities 
of  eusol  is  to  make  it  up  from  liquor  calcis  chlorinatse,  that  is  10 
per  cent,  chloride  of  lime ;  this  solution,  contrary  to  the  statement 
in  the  Pharmacopoeia,  keeps  very  well  if  stored  in  a  cool  dark  cup- 
board. I  have  kept  it  for  months  in  the  laboratory  with  a  very  small 
loss  of  chlorine.  This  solution  may  be  made  in  quantity,  say  two 
liters,  filtered  clear,  and  the  chlorine  content  determined;  the 
amount  necessary  for  one  liter  of  eusol  is  easily  calculated;  with  a 
4F.  W.  Andrews  and  K.  J.  P.  Orton,  Cent.  f.  Bakt.,  1903-4,  35,  Abt.  1, 
pp.  645  and  811. 
