52 
Current  Literature. 
Am.  Jour.  Pharm. 
January,  1920. 
of  concentrated  sulphuric  acid  when  the  first  reaction  has  ended. 
After  a  few  minutes,  lo  Cc.  of  water  are  added,  and  the  mixture  is 
heated  for  half  an  hour  to  gentle  boiling,  precautions  being  taken 
against  loss  by  spraying.  The  manganese  dioxide  is  then  removed 
by  a  slight  excess  of  hydrogen  peroxide,  30  Cc.  of  water  are  added, 
and  the  solution  is  again  boiled  for  ten  minutes,  after  which  a  dilute 
solution  of  potassium  permanganate  is  added  drop  by  drop  until 
a  faint,  permanent  pink  tinge  is  obtained.  This  is  discharged  by 
the  addition  of  a  drop  of  dilute  solution  of  oxalic  acid.  The  solution 
is  then  cooled,  2.5  Gm.  of  potassium  iodide  are  added,  the  whole 
being  allowed  to  remain  for  an  hour,  and  the  liberated  iodine  titrated 
by  means  of  thiosulphate.  A  blank  experiment  should  be  carried 
out  alongside  each  estimation,  and  the  final  reading  corrected  ac- 
cordingly.   The  following  are  examples  of  the  results  obtained: 
As. 
Substance.  Found.  Calc. 
3-Nitro-4-liydroxyphenylarsinic  Acid   28.4,  28.4  28.5 
^-Aminophenylarsinic  Acid   34-5,  34. 5  34.6 
I  :  2-Dihydrobenzoxazolone-4-arsinic  Acid..   28.6  28.9 
3-Nitro-4-aminophenylarsinic  Acid   28.9,  28.8  28.6 
3  :  3'-Dimtro-4  :  4'-dihydroxydiphenylarsinic  Acid....  19.6,   19.5  19.5 
^-Bromophenylarsinic  Acid   26.5  26.7 
(From  The  Analyst,  November,  1919.) 
Analysis  of  Vaseline. — G.  Armanni  and  A.  G.  Rodano  {Annali 
chim.  applic,  12:  50-51,  1919). — A  method  of  distinguishing  be- 
tween natural  and  artificial  vaseline  has  been  based  upon  the  different 
solubilities  of  the  two  substances  in  a  mixture  of  benzene  and  abso- 
lute alcohol  (i  :  i).  One  part  of  the  vaseline  is  dissolved  in  20  parts 
of  the  hot  solvent,  and  the  solution  allowed  to  stand  for  twenty- 
four  hours  in  a  cold  place.  If  the  vaseline  be  natural,  there  will 
only  be  a  slight  oily  deposit,  while  artificial  vaseline  yields  a  flocculent 
or  crystalline  deposit  resembling  paraffin  wax.  In  the  case  of  mix- 
tures the  amount  of  precipitate  is  proportional  to  the  quantity  of 
artificial  vaseline  present,  and  the  method  will  detect  less  than  20 
per  cent,  of  the  latter.    (From  The  Analyst,  November,  191 9.) 
Microscopic  Diagnosis  of  Amebic  Dysentery. — For  the  fixation 
and  staining  of  amebas,  motile  and  encysted,  Haig  makes  thin 
smears  from  the  fresh  stool,  selecting,  where  present,  a  portion 
containing  mucus  and  blood,  on  cover  slips,  and  floated,  without 
