Am.  Jour.  Pharm. ) 
March,  1884.  J 
Soap  Manufacture  and  the  Soap  of  Commerce. 
143 
of  the  best  soaps  has  of  late  fallen  off  considerably,  and  the  cheaper 
kinds  have  taken  their  place. 
Although  I  have  used  the  term  pure  soap  to  represent  a  soap  manu- 
factured from  fat  and  alkali  alone,  it  would  be  unfair  to  designate  the 
common  soaps  adulterated,  as  we  shall  see  on  considering  their  nature. 
A  pure  tallow  soap  will  only  take  a  certain  proportion  of  water,  and 
it  becomes  necessary  to  mix  other  substances  with  it  if  the  percentage 
of  water  is  increased.  A  substance  which  is  useful  in  this  respect,  and 
which  at  the  same  time  has  detergent  properties,  is  silicate,  of  soda. 
This  is  the  substance  known  as  soluble  glass,  but  it  is  usually  sold  to  the 
soap  bojjer  in  solution.  It  is  composed  of  silicic  acid  and  soda,  in 
various  proportions,  and  is  formed  of  two  kinds,  the  neutral  and  the 
caustic.  The  neutral  has  a  specific  gravity  of  about  1*370,  and  con- 
tains about  65  per  cent,  of  water.  The  proportion  of  silicic  acid  is 
about  26  per  cent.,  and  the  remainder  is  soda  and  impurities.  The 
caustic  silicate  is  a  much  heavier  solution,  and  has  a  specific  gravity  of 
of  about  1'700.  It  contains  about  43  per  cent,  of  water,  33  per  cent, 
of  silicic  acid  and  the  remainder  alkali  and  impurities. 
These  solutions  are  either  used  alone,  or  in  combination,  and  are 
added  to  the  soap  before  finishing.  It  is  necessary  to  "  crutch  "  well 
to  insure  the  complete  mixing,  and  the  crutching  should  be  continued 
until  the  soap  is  about  to  set.  The  silicated  soaps  generally  contain  a 
larger  proportion  of  water  than  pure  soaps,  besides  the  actual  weight 
of  silicate,  and  they  can,  therefore,  be  produced  at  lower  prices.  The 
detergent  power  of  these  soaps  is  greater  than  would  be  indicated  by 
the  pure  soap  contained  in  them,  and  in  many  districts  this  variety  finds 
a  market  more  readily  than  the  better  qualities.  I  should  here  point 
out  that  the  value  of  a  soap  is  not  altogether  determined  by  the  com- 
position. A  pure  soap  may  be  produced  from  a  discolored  tallow  or 
oil,  which  as  a  rule  injures  the  appearance  and  causes  it  to  command  a 
less  value  in  the  market. 
A  form  of  silicated  soap  which  obtains  a  large  sale  is  the  mottled. 
This  differs  essentially  from  the  mottled  soap  manufactured  a  few  years 
back,  which  was  pure  and  necessarily  of  a  high  standard.  It  is  usually 
manufactured  from  bleached  palm  oil,  or  from  palm  nut  oil  or  cocoa 
nut  oil  as  the  chief  ingredient.  It  is  usually  run  with  silicate  to  a 
considerable  extent  and  contains  a  variable  amount  of  fatty  acids — the 
quantity  depending  on  the  quality  it  is  desired  to  make.   The  mottling 
