494 
Soluble  Essence  of  Ginger. 
Am.  Jour.  Pharm. 
Oct.,  1878. 
tudinally,  only  a  very  slight  blue  coloration  may  be  perceived.  Water 
containing  only  some  tenths  of  a  milligram  of  nitrous  acid  per  liter 
will  certainly  destroy  the  color  in  an  hour.  The  rapidity  and  distinct- 
ness of  the  reaction  are  remarkably  increased  on  heating  the  liquid 
mixture  gently  for  a  short  time.  Solutions  of  potassium  nitrate,  con- 
taining one-tenth  of  a  millionth  of  nitrous  acid  per  cc.  are  decolor- 
ized in  a  few  minutes  after  being  gently  heated.  A  strong  and  pro- 
longed heat  is  to  be  avoided.  Attempts  made  at  the  titration  of  nitrous 
acid  by  means  of  the  blue  molybdic  solution,  have  so  far  given  unsat- 
isfactory results.  Still  if  we  admit  that  1  mol.  of  permanganic  acid 
corresponds  to  5  mols.  of  molydic  oxide,  it  is  easy  to  determine  with 
precision  the  quantity  of  molybdic  oxide  contained  in  a  liquid  by  titra- 
tion with  permanganate.  It  might  therefore  be  possible  to  determine 
nitrous  acid  in  a  satisfactory  manner  by  causing  the  blue  solution  of 
molybdic  acid  to  react  for  a  certain  time,  the  length  of  which  must  be 
experimentally  determined,  and  then  titrating  back  with  permanganate. 
The  blue  solution  is  not  very  stable. — Cbem,  News  [Lond.],  July  12, 
1878,  from  Zeitschrift  fur  Anal.  Chemie. 
SOLUBLE  ESSENCE  OF  GINGER.1 
By  J.  C.  Thresh,  Pharmaceutical  Chemist. 
Requiring  some  time  ago  a  strong  solution  of  the  active  principles 
of  ginger  which  would  mix  with  water  or  syrup  without  causing 
turbidity,  I  was  led  to  make  a  number  of  inquiries  and  experiments, 
some  of  the  results  of  which  it  is  the  purpose  of  this  paper  to  com- 
municate. 
I  found  that  most  wholesale  drug  houses  made  and  kept  in  stock 
a  so-called  soluble  ginger  essence,  but  in  many  cases  the  pungency  was 
due  to  cayenne,  and  (with  one  exception)  the  pleasing  aroma  of  ginger 
was  woefully  deficient. 
I  also  obtained  several  receipts  for  this  essence,  but  none  of  them 
gave  satisfactory  results.  One  ordered  the  powdered  root  to  be  per- 
colated with  a  dilute  alcohol,  another  with  a  mixture  of  spirit  and 
glycerin,  a  third  ordered  a  strong  decoction  of  the  ginger  to  be  fortified 
and  preserved  by  the  addition  of  a  weak  tincture  of  cayenne,  etc.,  but 
not  one  of  them  yielded  a  result  possessing  the  full  flavor  and  odor  of 
the  ginger  from  which  it  had  been  prepared. 
1  Read  before  the  British  Pharmaceutical  Conference. 
