360 
Petrolatum  Liquidum,  U.  S.  P.  VI IL  {K\*™£v&™' 
PETROLATUM  LIQUIDUM,  U.  S.  P.  VIII  (PARAFFINUM 
LIQUIDUM),  WHITE  MINERAL  OIL. 
By  S.  L.  Hilton. 
The  U.  S.  P.  VIII  provides  that  this  substance  shall  conform  to 
the  following  description : 
A  mixture  of  hydrocarbons,  chiefly  of  the  methane  series,  obtained 
by  distilling  off  most  ,of  the  higher  and  more  volatile  portions  from 
petroleum  and  purifying  the  liquid  residue. 
A  colorless,  or  very  slightly  yellowish,  oily,  transparent  liquid 
without  odor  or  taste,  but  giving  off,  when  heated,  a  faint  odor  of 
petroleum. 
Sp.  gr.  .870  to  .940  at  25 0  C.  Tests  as  to  solubility,  acid  impuri- 
ties, fixed  oils  or  fats,  either  animal  or  vegetable,  and  readily  carbon- 
izable  impurities. 
It  is  proposed  for  the  U.  S.  P.  IX  to  change  the  official  title  to 
Paraffinum  Liquidum.  This  seems  to  be  wise  and  in  conformity 
to  modern  standards.  The  description,  allowing  a  very  slight  yellow 
color,  is  a  mistake,  as  there  is  no  difficulty  in  obtaining  a  colorless  oil 
except  the  oils  of  this  kind  that  are  produced  in  this  country.  The 
new  requirement  which  requires  that  it  shall  be  free  from  fluorescence 
is  proper  and  not  unnecessarily  exacting. 
From  a  careful  study  of  a  number  of  samples  of  white  mineral  oil, 
obtained  from  various  sources,  the  appended  table  shows  that  the 
official  requirements  can  be  met  without  much  difficulty ;  it  is  further 
demonstrated  that  an  oil  that  is  usually  above  the  sp.  gr.  .870  will 
show  more  or  less  paraffin  when  subjected  to  a  temperature  of  — 40 
C,  yet  in  the  table  two  samples,  each  of  the  sp.  gr.  of  .875,  remained 
perfectly  clear  after  being  subjected  to  this  temperature  for  eight 
hours.  It  is  therefore  evident  that  in  the  process  of  purification 
chilling  was  not  thorough  or  carried  on  for  a  sufficient  length 
of  time,  and  the  final  filtration  was  not  performed  at  the  same 
temperature.  The  desire  to  have  as  heavy  oil  as  possible  for  internal 
administration,  as  recommended  by  Dr.  Lane,  of  London,  is  no  doubt 
accountable  for  such  a  large  number  of  samples  with  a  specific 
gravity  lower  than  .875  becoming  opaque  or  milky  at  this  temperature. 
With  proper  manipulation  and  care  an  oil  of  the  sp.  gr.  .8755 
should  show  no  separation  of  paraffin  on  chilling.  Some  standard 
covering  this  point  should  be  provided ;  that  is,  a  minimum  specific 
