316  Analytical  Characteristics  of  Talcum.  \Am$™' 
Pharm. 
1921. 
THE  ANALYTICAL  CHARACTERISTICS  OF  POWDERED 
TALCUM  FOR  USE  IN  TOILET  ARTICLES. 
By  George  E.  £we. 
Talcum  is  used  for  very  many  commercial  purposes  such  as 
lubrication,  as  fillers  in  rubber  and  compositions  of  various  kinds, 
paper,  marking  pencils,  paints,  the  cleaning  of  textiles,  for  clarify- 
ing and  absorbent  processes,  etc.  The  chief  pharmaceutical  uses 
are :  for  toilet  talcum,  medicinal  dusting  powders,  face  powders, 
foot  powders,  as  a  lubricant  in  tablet  manufacture,  for  coating 
pills  and  as  a  clarifying  and  absorbent  agent. 
These  many  and  varied  uses  call  for  various  grades,  and,  as  a 
consequence,  the  market  affords  many  grades.  Therefore  the  estab- 
lishment of  suitable  standards  for  analytical  characteristics  for  the 
proper  selection  of  powdered  talcum  for  use  in  toilet  articles  be- 
comes a  specific  necessity  in  order  to  obtain  satisfactory  material. 
Originally  talcum  is  a  rock,  and  being  a  natural  product,  is 
subject  to  all  the  variations  in  quality  inherent  in  a  product  taken 
from  the  earth.  In  its  natural  location  it  is  associated  with  many 
different  kinds  of  mineral  substances,  all  of  which  are  harder  than 
itself,  talcum  being  practically  the  softest  of  all  minerals.  There- 
fore, in  selecting  talcum  for  toilet  articles  it  is  necessary  that  care 
be  taken  to  insure  the  absence  of  these  associated  substances,  which 
are  harder,  and  as  a  consequence,  harsher  to  the  touch. 
It  is  also  important  to  take  into  consideration  other  character- 
istics, such  as  fineness  of  subdivision,  whiteness,  feel  between  thumb 
and  forefinger,  adherence,  "pearliness,"  density,  sifting  quality, 
chemical  characteristics  and  freedom  from  dampness. 
Discussion  of  the  importance  of  each  characteristic  and  of 
the  method  of  employing  the  characteristic  as  a  means  of  selecting 
powdered  talcum  will  be  taken  up  in  the  case  of  each  characteristic 
mentioned  above. 
Harsh  Associated  Substances. — The  presence  of  these  sub- 
stances is  usually  made  evident  by  the  "thumb  and  forefinger"  test, 
which  consists  of  rubbing  a  pinch  of  the  powdered  material  between 
the  thumb  and  forefinger  and  carefully  noting  the  "feel."  The 
value  of  this  test  can  only  be  appreciated  after  extensive  compara- 
tive tests. 
