Am.  Jour.  Pharm.  \ 
April,  1 918.  ■> 
Current  Literature. 
301 
graduated  cylinder,  and  to  allow  the  liquids  to  separate.  In  the  case 
of  pure  castor  oil  the  increase  in  the  volume  of  the  oily  layer,  due  to 
solution  of  the  petroleum  spirit,  will  he  about  11  or  12  Cc,  but  in 
the  presence  of  foreign  oils  will  be  greater,  and  the  amount  of  in- 
crease affords  a  rapid  criterion  of  the  purity  of  the  oil.  After  com- 
plete separation,  50  Cc.  of  the  petroleum  spirit  layer  are  evaporated 
and  the  residue  weighed.  Twelve  samples  of  pure  castor  oil  yielded 
from  8.35  to  8.85  per  cent,  of  residue,  the  average  being  8.52  per 
cent.  By  deducting  the  average  figure  from  the  amount  of  residue 
obtained  from  a  mixture  it  is  possible  to  estimate  the  amount  of  for- 
eign oil  present.  For  example,  castor  oil  containing  30  per  cent,  of 
arachis  oil  yielded  38.61  per  cent,  of  residue ;  oil  containing  4  per 
cent,  yielded  12.73  per  cent. ;  and  oil  containing  1  per  cent,  of  arachis 
oil  yielded  10.04  Per  cent,  of  residue.  The  residue  from  the  petro- 
leum spirit  extract  is  suitable  for  the  estimation  of  arachidic  acid 
by  Bellier's  method. — C.  Frabot.  (Ann.  Chim.  Anal.,  1917,  22,  217- 
223.)    From  The  Analyst. 
Use  of  Textile  Fibers  in  Microscopic  Qualitative  Analysis. 
— Fibers  from  flax,  cotton,  viscose  silk  (cellulose  xanthate),  lustron 
silk  (cellulose  acetate),  gelatin  silk,  wool,  mohair,  and  true  silk, 
were  tested  with  litmus  in  neutral  acid,  and  alkaline  solutions.  Silk 
was  found  to  be  the  most  satisfactory  in  every  respect,  the  particular 
kind  of  silk  having  little  or  no  effect  on  the  results.  The  sensitive- 
ness of  litmus  silk  depends  on  the  degree  of  adsorption  of  the  dye, 
and  on  the  degree  of  purification  of  the  raw  silk  and  of  the  litmus. 
Silk  fibers  may  also  be  used  as  carriers  for  lacmoid,  but  this  is  less 
sensitive  than  litmus.  The  sensitized  fibers  are  examined  micro- 
scopically for  change  of  color  when  partially  immersed  in  a  drop 
of  the  fluid  under  examination  on  a  slide.  Litmus  silk  fibers  can 
be  used  for  the  detection  of  either  acid  or  alkali,  while  Congo  red 
viscose  silk  fibers  can  only  be  used  for  the  detection  of  acidity.  In 
the  case  of  mineral  acids  a  solution  as  dilute  as  N/4500  will  give  a 
positive  reaction  with  litmus  silk;  acetic  acid  fails  beyond  N/100; 
the  fibers  are  not  quite  so  sensitive  to  alkali.  Congo  red  fibers  can- 
not be  used  to  differentiate  organic  acids  from  mineral  acids.  Elab- 
orate directions  based  on  Wartha's  procedure  {Ber.,  1876,  9,  217) 
are  given  for  the  preparation  of  extremely  pure  litmus  reagent.  The 
most  sensitive  silk  threads  for  use  with  litmus  were  those  that  had 
been  treated  by  a  preliminary  boiling  for  one  hour  in  a  2  per  cent. 
