596 
Colloidal  Metals. 
f  Am.  Jour.  Pharm. 
i     August,  19 18. 
first  prepared,  but  its  therapeutic  application  dates  back  only  to  1896, 
when,  under  the  name  of  collargol,  a  colloidal  preparation  of  silver 
was  introduced  by  Crede  as  an  antiseptic.  This  substance,  which 
occurs  in  small  black  scales  having  a  metallic  lustre,  forms  with 
water  an  opaque  solution,  which  has  all  the  properties  of  a-  colloid. 
Although  a  colloid,  however,  collargol  is  not  really  a  colloidal  metal, 
but  it  is  generally  considered  to  be  a  combination  of  an  acid  silver 
molecule  with  ammonia,  i.  e.,  collargolate  of  ammonia.  Somewhat 
later,  Trillet  succeeded  in  preparing  oxydases  of  certain  metals  by 
precipitating  solutions  of  metallic  salts  with  an  alkali  in  presence  of 
albumin,  forming  a  kind  of  colloidal  solution  of  the  metals. 
Still  later,  Bredig  produced  the  solutions  known  by  his  name. 
These  are  true  colloidal  solutions  of  metals,  and  are  produced  by 
passing  an  electric  spark  through  pure  water  between  electrodes  of 
the  metal  to  be  dissolved.  The  electric  current  diffuses  a  minute 
quantity  of  the  metal  throughout  the  liquid — the  metal,  in  effect, 
becomes  volatilized  in  the  liquid.  The  resulting  solution  in  every 
case  is  a  dichroic  liquid,  transparent  to  transmitted  light  and  opaque 
to  reflected  light.  Suspended  particles  cannot  be  detected  by  ordi- 
nary methods,  and  the  solution  in  all  respects  obeys  the  rules  laid 
down  for  colloidal  substances.  The  metal  is  in  a  state  of  very  minute 
subdivision,  and  the  particles  possess  that  vibratory  motion  known 
as  "  Brownian  movement."  It  is  to  this  movement  and  to  the 
minuteness  of  the  metallic  corpuscles  that  the  catalytic  action  of 
Bredig's  liquids  is  due.  Different  metals  have  been  used,  but  it  has 
been  found  that  the  nature  of  the  metal  is  immaterial,  the  catalytic 
action  of  the  liquid  being  due  to  the  physical  condition  of  the  metal, 
and  not  to  the  metal  itself. 
Introduced  into  the  system,  these  solutions  produce  remarkable 
physiological  effects,  effects  that  have  been  shown  to  be  due  entirely 
to  the  physical  state  of  the  metal,  and  are  probably  connected  in 
some  way  with  its  electric  condition.  Their  use  in  therapeutics  is 
thus  indicated. 
With  the  object  of  arriving  at  some  definite  knowledge  of  the 
therapeutic  value  of  these  preparations,  Robin  and  Bardet  started 
in  1901  an  extended  series  of  trials,  chemical,  biological,  and  clin- 
ical, with  these  preparations.  The  oxydases  of  Trillet  were  found 
to  be  unsuitable  for  use  in  medicine ;  their  powers  of  oxidation  were 
unmistakable,  but  owing  to  their  alkaline  nature  they  produced 
necrosis  in  the  tissues  when  injected,  and  had  therefore  to  be  aban- 
