Am.  Jour.  Pharm.  \ 
November,  19 19.  > 
Purified  Ether. 
739 
deposit  and  become  a  brilliant  solution.  An  acid  mixture  consisting 
of  40  Cc.  nitric  acid,  5  Cc.  sulphuric  acid,  and  55  Cc.  of  water  is  re- 
quired for  dissolving  the  precipitate,  and  a  standard  solution  of 
sulphocyanide,  of  which  1  Cc.  will  be  equivalent  to  1  Mgm.  of  mer- 
cury (about  1  Gm.  KSCN  per  liter).  The  adaptation  used  is  as 
follows: — 1.08  Gm.  of  mercuric  oxide  is  taken,  mixed  with  a  little 
water,  dissolved  by  the  aid  of  nitric  acid,  and  then  diluted  to  a  liter 
— 1  Cc.  is  equivalent  to  1  Mgm.  Hg.  Twenty-five  Cc.  of  this  solu- 
tion are  mixed  with  1 5  Cc.  of  the  "  acid  mixture  "  and  2  Cc.  of  a 
saturated  solution  of  iron  alum,  and  then  titrated  with  the  sulpho- 
cyanide solution ;  a  reddish-brown  tint  marking  the  end  point.  The 
value  of  the  sulphocyanide  in  terms  of  mercury  is  thus  obtained  by 
a  simple  calculation.  It  is  to  be  remembered  that  the  presence  of 
chlorides  would  vitiate  this  reaction. 
In  testing  rectified  ether  8  Cc.  may  be  taken,  but  with  methylated 
only  4  Cc,  and  with  ordinary  720  methylated  (not  purified)  2  Cc.  is 
sufficient.  About  75  Cc.  of  distilled  water  is  taken  in  a  100  Cc.  grad- 
uated flask,  and  10  Cc.  of  2  per  cent,  silver  nitrate  solution,  the  ether 
is  added,  and  the  whole  shaken  till  it  is  dissolved ;  2  Cc.  of  20  pier 
cent,  caustic  soda  solution  are  now  run  in,  and  the  volume  adjusted 
to  100  Cc.  The  flask  is  stoppered,  inverted  once  or  twice,  and  set 
aside  for  a  minute  or  two ;  it  is  then  vigorously  shaken  continuously 
for  three  minutes  and  then  filtered.  This  treatment  removes  the 
aldehyde.  The  shaking  is  very  necessary  as  otherwise  traces  of 
silver  remain  in  colloidal  suspension.  Fifty  Cc.  of  the  reagent  are 
placed  in  a  conical  flask,  and  then  75,  50  or  25  Cc.  of  the  ether  filtrate 
added  according  to  the  supposed  contamination,  but  having  rather 
less  than  2  Mgm.  of  aectone  to  the  50  Cc.  of  reagent.  The  contents 
of  the  flask  are  thoroughly  mixed,  and  a  strong  white  turbidity  ap- 
pears within  a  second  or  two  if  any  quantity  of  ketone  is  present. 
The  flask  is  set  aside  over  night,  and  in  the  morning  the  clear  super- 
natant liquid  carefully  poured  off  under  suction  through  a  Gooch 
crucible  which  carries  a  moderately  thick  mat  of  pulped  filter  paper. 
(Whatman's  41  answers  very  effectively.)  The  precipitate  is  then 
washed  on  to  the  filter,  and  thoroughly  cleansed  with  water  till  free 
from  alkali.  The  filter  mat  and  precipitate  are  then  transferred  to 
the  original  flask,  disintegrated  in  a  few  Cc.  of  water,  and  then 
treated  with  15  Cc.  of  the  acid  mixture  and  2  or  3  Cc.  of  -ft  per- 
manganate to  help  in  the  oxidation.  The  flask  is  either  set  on  the 
steam  bath  for  a  quarter  of  an  hour,  or  boiled  for  one  or  two  min- 
