264  Analytical  Researches  and  Investigations.  {^^'^IT'^^^^"^' 
On  the  Detection  of  Urea  by  means  of  Oxalic  Acid.  By  E.  Briicke. 
- — The  detection  of  urea  may  be  very  accurately  effected  if  this  body  is 
finally  taken  up  with  aniylic  alcohol,  and  precipitated  by  a  solution  of 
oxalic  acid  in  amylic  alcohol.  The  crystals  of  oxalate  of  urea  are 
usually  small,  but  are  better  developed  when  the  entire  liquid  is 
warmed  until  the  crystals  have  dissolved  and  then  allowed  to  cool. 
The  amylic  alcohol  solution  which  is  to  be  tested  for  urea  may  also  be 
precipitated  by  a  solution  of  oxalic  acid  in  anhydrous  ether.  This 
latter  mode  of  procedure  would  be  adapted  to  its  quantitative  estima- 
tion, as  the  separation  of  the  oxalate  of  urea  thus  proceeds  very 
rapidly.— I6id,  p.  364,  from  C.  Bl  med.  Wiss.,  1883,  p.  139. 
The  Separ^ation  of  Citric  and  Tartainc  Acids.  By  C.  Rovera. — The 
solution  of  the  mixture  of  both  acids  is  neutralized  with  sodium  car- 
bonate, the  carbonic  acid  expelled  by  boiling,  and  the  solution  sub- 
sequently made  slightly  but  perceptibly  acid  by  the  addition  of  a 
very  small  amount  of  the  respective  acid  mixture.  A  solution  of 
calcium  chloride  is  then  added,  whereby  the  tartaric  acid  is  completely 
separated,  and  from  the  filtrate  the  citric  acid  is  separated  as  calcium 
citrate  when  the  liquid  is  heated  to  boiling. — Ibid.,  No.  26,  1883,  p. 
393,  from  Giorn.  Farm.  Chim.,  32,  p.  60. 
The  Estimation  of  Mineral  Oil  in  Fats  and  Resins.  By  A.  Gawa- 
lowski. — Twenty  grams  of  the  fat  or  resin  are  saponified  in  a  large 
porcelain  capsule  Avith  a  solution  of  fifteen  to  twenty  grams  of  caustic 
potassa  in  100  to  150  cubic  centimeters  of  water,  and  the  soapy 
mixture  finally  evaporated  at  a  gentle  heat  to  dryness.  The  soap 
residue  is  then  dissolved  in  lukewarm  water,  the  solution  brought  into 
a  separating  funnel,  and,  after  cooling,  shaken  with  ten  to  fifteen  cubic 
centimeters  of  petroleum  ether.  After  standing  for  six  or  eight  hours 
the  clear  lower  liquid  is  decanted,  the  petroleum  ether  layer  is 
repeatedly  washed  with  lukewarm  water  until  a  portion  of  the 
separated  wash  water  no  longer  froths  upon  agitation,  and  the  com- 
bined soap  lyes  decomposed  with  dilute  sulphuric  acid.  The  fatty 
acids  which  are  thereby  liberated  are  extracted  with  ether,  and  freed 
from  the  latter  by  evaporation.  The  original  petroleum  ether  layer  is 
allowed  to  evaporate  at  a  gentle  heat,  dried  over  sulphuric  acid  or  in 
an  air-bath,  and  the  residual  mineral  oil  weighed. 
Comparative  experiments  with  known  mixtures  of  mineral  oils  with 
saponifiable  fats,  afforded  perfectly  satisfactory  results. — Ibid.,  from 
Rundschau  and.  Wiec¥s  Gew.,  Ztg.,  48,  p.  74. 
