-Am.  Jour.  Pharm. 
June,  1897. 
Spirit  of  Nitrous  Ether. 
ments  of  the  normal  epidermis  for  the  stomata.  If  many  are  found 
that  are  quite  round  in  outline  (b,  Fig.  4),  the  presence  of  Alexan- 
dria senna  is  assured.  As  confirmatory  to  this,  the  number  of  hair 
scars  upon  the  epidermal  fragments  may  be  employed.  These 
should  be  found  frequently  at  a  distance  of  from  two  to  five  epider- 
mal cells  apart.  A  sample  of  India  senna,  on  the  contrary,  will 
exhibit  few  hairs,  often  none  in  the  field,  and  the  great  majority  of 
the  stomata  will  be  found  with  the  long  diameter  much  longer  than 
the  short  one  (b,  Fig.  /).  The  hairs  should  not  frequently  be  closer 
than  five  epidermal  cells  apart.  In  simple  powders  the  mere 
number  of  hairs  present  will  at  once  distinguish  between  the  two 
sennas,  but  in  cases  of  mixture  of  the  two,  the  shape  of  the  stomata 
will  have  to  be  examined.  Many  of  the  elongated  oval  form  always 
indicate  the  presence  of  India  senna. 
However  good  a  test  may  be  theoretically,  it  is  of  no  value  unless 
it  works  practically.  The  only  way  to  tell  whether  it  will  do  this 
or  not,  is  to  put  it  in  practice  under  conditions  which  will  represent, 
as  nearly  as  may  be,  those  of  its  usual  employment.  In  this  par- 
ticular instance  the  test  proposed  was  given  a  thorough  trial  in  the 
hands  of  eighteen  students  of  representative  abilities,  and  in  no  case 
did  it  fail  to  work,  either  with  simple  powders  or  mixtures. 
1/ 
ASSAY  OF  SPIRIT  OF  NITROUS  ETHER. 
By  Lawrence  A.  Kessler,  Ph.G. 
Contribution  from  the  Chemical  Laboratory  of  the  Philadelphia  College  of 
Pharmacy.    No.  167. 
My  attention  was  attracted  to  this  subject  by  a  series  of  papers 
which  appeared  in  the  American  Druggist  and  Pharmaceutical 
Record.  To  the  number  of  that  journal  for  December  25,  1895, 
Professor  David  Walker  contributed  an  article  in  which  he  pro- 
posed a  rapid  method  for  the  volumetric  assay  of  spirit  of  nitrous 
ether.  His  process  of  assaying  was  based  on  the  measurement  of 
the  iodine  liberated  from  potassium  iodide,  through  the  decompo- 
sition of  spirit  of  nitrous  ether  by  the  United  States  Pharmacopoeia 
process  of  assay. 
The  proposed  test  was  made  by  carefully  measuring  5  c.c.  of 
spirit  of  nitrous  ether  into  a  4-ounce  Erlenmeyer  flask,  from  a 
pipette ;  this  was  followed  with  10  c.c.  of  6  per  cent,  acetic  acid  and 
