Am.  Jour.  Pharm. 
Sept.  1919. 
Colloidal  Metals. 
625 
Experiments  have  also  been  carried  out  on  a  large  scale  using 
cane  sugar  and  starch  glucose  as  fermentable  material.  It  was 
found,  however,  necessary  in  these  cases  to  employ  yeast  foods  in 
quantities  that  deleteriously  influenced  the  purification  of  the 
glycerin.  It  was  therefore  concluded  that  these  materials  possess 
no  superiority  over  molasses  for  the  purpose. 
Since  the  process  of  producing  glycerin  by  fermentation  is  in  its 
present  state  of  development  restricted  to  molasses,  the  writer 
would  point  out  that  in  some  parts  of  the  world,  notably  in  Aus- 
tralia and  Fiji,  molasses  is  a  waste  product  which  is  run  out  to  sea. 
The  present  process  should,  therefore,  be  of  great  significance  in 
such  countries.  There  are  several  details  in  this  process,  as  out- 
lined in  the  report,  which  in  the  writer's  opinion  are  open  to  criti- 
cism. As,  however,  a  year  has  elapsed  since  the  report  was  officially 
handed  in,  further  developments  may  have  eliminated  the  appli- 
cability of  these  criticisms. 
COLLOIDAL  METALS:  THEIR  PREPARATION  AND 
PROPERTIES.1 
By  Thos.  Stephenson,  F.R.S.  Edin. 
The  use  of  colloidal  substances  in  medicine  is  of  comparatively 
recent  introduction,  and  now  that  knowledge  of  their  properties  and 
action  is  more  exact,  their  employment  in  the  treatment  of  disease 
is  increasing  rapidly.  It  is  intended  here  to  give  merely  a  general 
sketch  of  the  colloidal  preparations  in  more  general  use :  for  details 
of  the  various  varieties  of  colloids  readers  are  referred  to  the  very 
complete  section  on  this  subject  in  the  Extra  Pharmacopoeia  by 
Martindale  and  Westcott  (16th  edit.,  p.  308). 
The  term  "  colloid  "  (from  KoXXa,  glue)  was  first  used  by  Thomas 
Graham  to  distinguish  those  amorphous  substances,  of  which  glue 
and  gelatin  are  typical  examples,  which  diffuse  with  difficulty 
through  membranes,  as  opposed  to  "  crystalloids,"  which  diffuse 
with  ease.  The  word  is  now  used  to  describe  a  condition  which 
chemical  substances  may  be  made  to  assume,  rather  than  to  define 
a  particular  class  of  compounds.  A  colloidal  solution  is  in  reality  a 
suspension  of  minute  particles  of  the  substance.   These  particles  are 
1  Reprinted  from  The  Prescriber,  June,  1919. 
