^AiTtassr'l      Practical  Notes  from  Various  Sources.  407 
ash,  the  sulphocjanide  of  sinapine  and  the  myrosine,  we  find  nitrogen, 
5'342  per  cent.,  and  sulphnr,  1*50  per  cent. 
If  the  amounts  of  the  three  last-named  constituents  of  the  mustard 
be  deduced  from  the  total  amounts  of  nitrogen  and  sulphur,  according 
to  Hassall,  the  following  will  be  the  percentages : 
Myronate  of  potash,  .  .  .     0"61  per  cent. 
Sulphocyanide  of  sinapine,  .  .         10-71  " 
Myrosine,   .  .  .  .  .    28-52  " 
In  this  case,  the  results  obtained  by  calculation  fr^m  the  j)ercentages 
of  nitrogen  and  sulphur  are  almost  identical  Avith  those  obtained  by 
direct  determinations.  But  the  greater  ease  and  certainty  of  the  direct 
method,  and  the  very  considerable  errors  which  are  possible  when  cal- 
culations are  instituted  upon  results  differing  but  very  slightly  from 
the  true  ones,  must  strongly  recommend,  it  appears  to  us,  the  direct  as 
compared  with  the  indirect  method. 
If  the  mustard  is  adulterated  with  starch  or  flour,  the  foregoing 
scheaie  of  analysis  may  be  used  as  w^ell  in  the  case  of  pure  mustard. 
After  the  extraction  of  the  oil  with  ether,  and  the  sulphocyanide  of 
sinapine  and  myronate  of  potash  with  alcohol,  the  residue  may  be 
treated  either  with  malt  extract  or  with  acids  under  pressure  to  con- 
vert the  starch  into  glucose.    The  glucose  may  be  estimated  as  usual. 
Fearing  that  starch  was  not  entirely  insoluble  in  dilute  alcohol,  and 
not  being  able  to  learn  anything  on  the  subject  from  books,  an  experi- 
ment was  made  of  boiling  starch  for  some  time  in  a  mixture  of  half 
alcohol  and  half  water.  The  boiling  liquid  was  filtered  hot,  and  to 
the  filtrate  a  few  drops  of  iodine  solution  added.  No  blue  coloration 
taking  place,  the  starch  may  be  considered  insoluble  in  dilute  alcohol, 
and  hence  could  not  interfere  in  the  determination  of  the  sulj^hocya- 
nide  of  sinapine  and  myronate  of  potash. — Jour.  Am.  Chem.  Soc, 
1881,  p.  130. 
PEACTICAL  NOTES  FROM  VARIOUS  SOURCES. 
By  the  Editor. 
For  the  rapid  preparation  of  Oxygen  Voracek  recommends  adding 
hydrogen  peroxide  to  potassium  permanganate  when  the  evolntion 
takes  place  at  the  common  temperature  and  without  requiring  special 
caution.  According  to  ^^Industrie-Blatter,"  No.  15,  a  much  cheaper 
source  is  barium  peroxide,  to  15  grams  of  Avhich  are  added  100  cc.  of 
a  mixture  of  equal  volumes  of  concentrated  potassium  bichromate 
