%S;SM'}       The  Action,  etc.  of  Disinfectants.  503 
I  believe  it  is  quite  possible  to  do  so,  certainly  with  some  if  not 
with  all  extracts. 
I  find  that  extracts  of  fair  average  consistence  for  pill-making, 
when  subjected  to  the  heat  of  a  water-bath,  in  the  cases  of  belladonna 
and  hyoscyamus  lose  20  per  cent,  of  their  weight,  and  in  the  case  of 
conium,  25  per  cent. 
The  plan  I  adopted  was  to  spread  the  extract  very  thinly  on  a  thin 
platinum  capsule,  and  dry  at  a  temperature  of  212°  until  it  ceased  to 
lose  weight.  Various  experiments  with  the  same  extract  gave  in  this 
way  very  constant  results.  At  first  I  operated  on  quantities  of  10 
grains  at  a  time,  but  I  found  that  several  hours  were  then  required 
for  complete  desiccation,  whereas  if  only  one  or  two  grains  were  used 
the  time  required  was  little  more  than  half  an  hour. 
The  consistence  of  extracts  varies  so  much  that  it  would  seem  ad- 
visable to  define  in  the  Pharmacopoeia  the  amount  of  water  each 
should  contain,  the  amount  to  be  determined  as  I  have  recommended. 
When  once  a]  standard  has  been  set  up  there  would  be  practically 
little  difficulty  to  manufacturers,  for  I  find  after  a  few  trials  the  eye 
can  determine  from  the  consistence  of  the  extract,  to  less  than  1  per 
cent.,  the  amount  of  water  present. — Pharm.  Journ.  (Lond.\  Oct. 
.11,  1873. 
THE  ACTION  AND  RELATIVE  VALUE  OP  DISINFECTANTS* 
By  J.  A.  Wanklyn. 
If  we  heat  the  infectious  material  of,  for  instance,  scarlet  fever  to 
a  red  heat,  we  destroy  it.  There  can  be  as  little  doubt  that,  if  we 
bring  chlorine  gas  thoroughly  into  contact  with  infectious  material, 
we  destroy  it  likewise.  If  we  boil  it  with  oil  of  vitriol,  or  with  per- 
manganate of  potash,  we  destroy  it.  Probably,  too,  if  we  soak  it  in 
concentrated  carbolic  acid,  or  treat  it  with  excess  of  corrosive  subli- 
mate or  arsenious  acid,  we  render  it  inert.  It  is,  indeed,  highly  pro- 
bable that  every  kind  of  infectious  material  is  capable  of  being  ren- 
dered inert  by  thorough  contact  with  any  powerful  chemical  reagent. 
But  if  the  heat  be  only  gentle,  and  if  the  chemical  agent  be  dilute, 
*  Read  before  the  Public  Medicine  Section  at  the  Annual  Meeting  of  the 
•  British  Medical  Association  in  London,  August,  1873,  and  printed  in  the 
"British  Medical  Journal." 
