Am.  Jour.  Pharm.  ) 
August,  1920.  f 
Current  Literature. 
597 
Division,  U.  S.  Bureau  of  Chemistry,  Washington,  D.  C.  (through 
J.  Amer.  Chem.  Soc,  June,  1920). 
Dktkction  of  Minute  Quantities  of  Petroleum  Spirit  in 
VegetabIvE  OiIvS. — A  number  of  methods  for  the  detection  of  petro- 
leum spirit  in  vegetable  oils  have  been  proposed.  A  careful  study 
of  these  has  shown  that  they  are  not  satisfactory,  but  it  has  been 
found  that  Nastjukoff's  formolite  reaction  may  be  appHed  success- 
fully for  the  purpose  as  follows: 
The  oil  (50-100  g.)  is  saponified  by  means  of  potassium  hy- 
droxide solution.  Distilled  water  and  pure  calcium  chloride  solu- 
tion are  added,  the  liquid  distilled  by  means  of  steam,  and  the  dis- 
tillate treated  with  40  per  cent,  formaldehyde  solution  and  a  few 
drops  of  concentrated  sulphuric  acid.  A  reddish  brown  film  colora- 
tion on  the  surface  of  the  liquid,  gradually  changing  to  deep  yellow, 
indicates  presence  of  petroleum  spirit.  If  a  few  drops  of  the  distillate 
are  added  to  water,  a  brilliant  interference  ring  of  optical  waves 
is  produced  on  the  surface  of  the  water;  this  ring  becomes  almost 
invisible  after  standing  for  some  time  and  disappears  completely 
on  heating.  With  soya  bean  oil  the  ring  does  not  change,  even  on 
heating.  The  above  process  is  capable  of  detecting  traces  of  petro- 
leum spirit  in  vegetable  oils,  and  may  be  made  the  basis  of  a  quan- 
titative method,  the  formolite  precipitate  being  weighed  after  dry- 
ing at  110-115°  C.  Masahiro  Aida.  (From  /.  Soc.  Chem.  Indus- 
try, June  15,  1920.) 
Cystine  Reaction. — Cystine,  whether  present  as  a  cystine 
calculus  or  in  any  other  form,  can  be  rapidly  and  easily  identified 
by  the  following  simple  test:  Place  a  small  portion  (not  more  than 
a  milligram)  on  a  slide,  moisten  with  a  droplet  of  strong  hydro- 
chloric acid  (s.  g.  1 . 17  to  1 . 18),  and  examine  under  the  microscope 
without  covering  with  a  cover-glass;  an  abundance  of  groups  of 
prismatic  needles  appear.  Add  a  droplet  of  water;  the  slide  clears. 
Evaporate  at  a  gentle  heat  to  dryness,  cool  thoroughly,  cover,  and 
add  a  droplet  of  water;  after  a  few  moments  hexagonal  plates  ap- 
pear.— Denig^s  {Bull.  Soc.  Pharm.  Bordeaux,  58,  8;  through  Pharm. 
Jour,  and  Pharmacist,  July  3,  1920). 
C01.ORLESS  Variety  of  Mercuric  Iodide. — Mercuric  iodide 
may  be  obtained,  temporarily,  in  colorless  crystals,  as  follows: 
About  10  Gms.  of  the  salt  is  placed  in  a  long  tube,  sealed  at  one  end, 
