414 
Theory  of  Diswfectants. 
<  Am.  Jour.  Pharm. 
I    Sept.  1, 1871. 
THE  THEORY  OF  DISINFECTANTS  * 
By  T.  p.  Blunt,  M.A.,  F.O.S. 
The  light  which  has  recently  been  thrown  upon  the  nature  of  con- 
tagion and  infection  by  the  labors  of  Pasteur  and  others,  the  results 
of  which  have  been  ably  summarized  by  the  President  of  the  British 
Association  in  his  late  inaugural  address  at  Liverpool,  seems  to  point 
the  way  to  clearer  and  more  coonprehensive  views  than  those  com- 
monly entertained  at  present  regarding  the  operation  of  the  substances 
known  as  disinfectants. 
These  may  be  divided  into  two  classes  : — 1.  Those  which  act  by  the 
oxidation  and  total  destruction  of  the  virus  contained  in  infected 
matters,  together  with  the  foul  gases  which  usually  accompany  it,  and 
which  are.  in  fact,  nature's  danger-signals  of  its  presence.  2.  Those 
substances  which  do  not  possess  the  active  chemical  properties  of  the 
first  class,  yet  are  proved  by  experience  to  have  a  similar  power  of 
arresting  and  checking  the  spread  of  infection.  The  latter  are,  for 
the  most  part,  the  more  ancient  and  popular,  having  apparently  in 
some  cases  been  suggested  by  a  just  but  unreasoning  instinct.  Thus 
we  find  that  the  use  of  sulphurous  acid,  as  evolved  from  burning  sul- 
phur, dates  even  from  Homeric  days ;  while  the  burning  of  pitch  and 
aromatic  gums  for  disinfectant  purposes  has  an  origin  at  least  equally 
remote. 
An  attempt  will  be  made,  in  the  course  of  the  observations  which 
follow,  to  bring  the  operation  of  the  large  majority  of  the  latter  class 
under  a  general  law  which  shall  furnish  us  with  an  explanation  of 
their  true  character.  This  is  especially  desirable,  since  it  is  to  be 
feared  that,  for  want  of  such  an  explanation,  many  good  and  valuable 
disinfectants  have  been  condemned  by  chemists,  on  theoretical 
grounds,  as  mere  deodorizers, — not  assailing  the  virus  of  infected 
substances,  but  rather  masking  their  poisonous  character  by  precipi- 
tating their  offensive  gases.  An  objection  to  this  view  at  once  meets 
us,  in  the  utter  disproportion  between  the  volume  of  the  gases  to  be 
fixed  and  the  quantity  of  salt  practically  found  sufficient  for  the  ob- 
ject required,  while  it  breaks  down  altogether  when  applied  to  such 
disinfectants  as  the  new  "chlor-alum"  or  chloride  of  aluminium  of 
Mr.  John  Gamgee,  or  the  well-known  carbolic  acid.    Before  endeav- 
*  Read  before  the  annual  meeting  of  the  Shropshire  Scientific  Branch  of  the 
British  Medical  Association. 
