Am.  Jour.  Pharm. 
July,  1884. 
Spiritus  JEtheris  Nitrosi. 
379 
stated  that  spirit  containing  3  per  cent,  of  ethyl  nitrite  fairly  repre- 
sented the  B.P.  preparation.  This  percentage  is  a  fair  one,  and  as  Dr. 
Dupre's  work  has  been  the  "  guiding  star  "  of  public  analysts,  we  may 
accept  his  standard,  especially  since  the  experience  of  practical  pharma- 
cists sufficiently  justifies  it.  Mr.  Symons  having  so  recently  shown 
("  Pharm.  Jour.,"  Oct.  13,  1883)  the  quality  of  commercial  spt.  sether. 
nit.,  I  have  not  attempted  the  collection  of  similar  information.  It 
was  necessary,  however,  to  determine  the  amount  of  ethyl  nitrite  pre- 
sent as  deterioration  proceeded,  and  for  this  purpose  Eykman's  method 
was  adopted,  others  having  proved  uncertain.  It  will  be  seen  from 
the  table  which  I  give  further  on  that  as  high  as  3*54  per  cent,  of 
ethyl  nitrite  was  found,  free  nitrous  acid  not  being  included  in  the 
percentage. 
The  Aldehyde  Content. — Aldehyde  has  generally  been  looked  upon 
as  an  unavoidable  contamination,  and  one  of  the  objects  aimed  at  by 
Professor  Redwood  in  devising  the  official  process  was  to  minimize  the 
yield  of  this  compound.  The  percentage  of  it  present  in  the  spirit  is 
variable,  and  as  it  is  closely  associated  with  ethyl  nitrite  in  deteriora- 
tion, I  shall  consider  it  in  the  paragraph  on  development  of  acidity.  In 
the  distillate  of  the  Pharmacopoeia  process  I  have  not  found  higher 
than  2  per  cent.  It  may  be  stated  that  the  method  of  estimation 
adopted  was  that  devised  by  Dr.  Thresh,1  which  is  based  on  the  forma- 
tion of  aldehyde  resin  with  excess  of  caustic  soda  solution,  the  colored 
solution  formed  being  diluted  to  the  tint  of  a  standard  aldehyde  resin 
solution,  and  compared  as  in  nesslerizing.  From  5  to  10  cc.  of  the 
spirit  may  be  used.  The  method  gives  fairly  constant  results,  and 
though  they  may  be  approximate,  still  they  are  much  more  constant 
than  those  given  by  Mr.  Rimmington's  •method,2  which  depends  on 
oxidation  of  the  aldehyde  with  hydroxyl  solution  and  subsequent 
titration  with  standard  alkali.  The  weakness  here  is  that  the  acidity 
produced  depends  on  more  than  aldehyde. 
These  two  bodies,  ethyl  nitrite  and  aldehyde,  are  the  leading  factors 
in  determining  the  deterioration  of  spiritus  retheris  nitrosi,  another 
being  their  solvent,  rectified  spirit,  a  mixture  of  alcohol  and  water. 
The  decomposition  which  results  in  the  mixture  of  these  three  bodies 
is  attended  by  at  least  three  marked  changes  which  can  be  physically 
and  chemically  determined  : 
1  "  Pharm.  Jour."  [3],  ix,  409. 
2  "  Pharm.  Jour."  [3],  x,  41. 
