3i8 
Disinfection. 
Am.  Jour.  Pharm. 
July,  1915.  . 
Group  3,  the  high  coefficient  disinfectants  which  also  emulsify 
when  mixed  with  water,  but  which  are  efficient  when  much  more 
highly  diluted. 
There  are  certain  advantages  in  using  these  coal-tar  derivatives 
which  make  them  far  superior  to  most  other  disinfectants.  These 
may  be  summarized  as  follows: 
Convenience. — Compared  with  dissolving  carbolic  acid  crystals  to 
make  a  three  to  five  per  cent,  solution  it  is  much  easier  to  dissolve 
any  member  of  these  groups.  Some  can  be  dissolved  in  water  in 
any  proportion ;  any  one,  if  properly  made,  can  be  dissolved  readily 
to  make  a  stronger  solution  than  is  possible  to  obtain  with  carbolic 
acid  crystals. 
Efficiency. — The  members  of  Group  I  will  dissolve  readily  to  make 
a  solution  of  any  desired  strength,  from  that  of  pure  carbolic  acid 
down  to  one  that  is  merely  antiseptic. 
The  members  of  Group  2  are  more  efficient — a  one  or  two  per 
cent,  solution  usually  far  exceeding  the  efficiency  of  the  strongest 
solution  of  phenol. 
The  members  of  Group  3  are  still  more  efficient,  as  their  phenol 
coefficients  indicate. 
Safety. — The  coal-tar  disinfectants  are  practically  neither  toxic 
nor  corrosive  when  diluted  for  use  on  the  basis  of  their  efficiencies. 
Character  of  Solution. — The  formula  for  almost  all  the  coal-tar 
disinfectants  is  such  that  the  solution  is  alkaline  and  soapy,  which 
aids  its  penetration.  There  is  very  little  if  any  coagulation  of  protein 
to  hinder  penetration  and  lower  the  efficiency. 
It  is  evident  from  the  above  comparisons  that  the  proper  use  of 
the  coal-tar  disinfectants  represents  a  distinct  advance  over  that  of 
carbolic  acid.  Even  the  one  factor  of  safety  alone  is  sufficient  reason 
to  exclude  the  latter  from  general  use. 
Comparing  the  coal-tar  disinfectants  with  those  of  the  metallic 
salts  and  gaseous  disinfectants,  the  most  important  point  to  be  con- 
sidered is: 
Adaptability. — Sulphites  and  sulphurous  acid  and  ferrous  salts 
are  strictly  limited  in  their  usefulness  to  such  conditions  where  the 
abstraction  of  oxygen  or  water  is  detrimental  or  destructive  to  the 
life  and  development  of  bacteria,  etc.  Calcium  hypochlorite  and 
potassium  permanganate  are  valuable  where  bacterial  life  is  endan- 
gered by  the  action  of  oxygen,  these  substances  being  oxidizing  agents 
either  directly  or  indirectly.    It  is  evident,  therefore,  that  such  sub- 
