SPIRIT  OF  NITROUS  ETHER  AND  NITRITE  OF  SODA.  357 
by  a  water-bath  at  140°  F.,  until  one-half  has  passed  over.  It 
has  a  specific  gravity  of  -900.  The  process  is  stated  to  be  that 
of  Wolfe,  and  has  been  found  by  Pelletier  to  succeed  better  than 
any  other. 
In  the  year  1839  the  Edinburgh  College  also  gave  a  process 
for  the  preparation  of  nitrous  ether,  but  simply  as  a  preliminary 
step  in  the  manufacture  of  spirit  of  nitrous  ether.  The  method 
directed  is  to  add  by  degrees,  through  a  safety  tube  in  a  mat- 
rass, 7  fl.  oz.  of  nitric  acid,  of  1*5  specific  gravity,  to  15  fl.  oz. 
of  rectified  spirit,  taking  care  that  the  action  is  not  too  violent, 
and  that  the  receiver  be  kept  cooled.  The  ether  thus  obtained 
is  purified  from  acid  by  a  little  milk  of  lime,  and  from  water  and 
spirit  by  a  concentrated  solution  of  chloride  of  calcium  (muriate  of 
lime.)  The  product  ("  pure  hyponitrous  ether  ")  thus  obtained 
should  have  a  density  -899.  This  is  then  mixed  with  four  times  its 
volume  of  rectified  spirit  (so  that  the  mixture  would  contain  20 
per  cent,  of  nitrous  ether),  and  the  resulting  spirit  of  nitrous 
ether  is  stated  to  have  the  specific  gravity  *847.  This  can 
hardly  be  correct,  as  the  density  of  rectified  spirit  is  -838,  and 
the  mean  of  the  volumes  above  will  yield  a,  result  of  -850.  The 
gravity  stated  by  the  Edinburgh  College  would  therefore  entail 
an  increase  of  volume  on  admixture  which  is  not  probable.  The 
test  given  for  the  strength  of  spiritus  setheris  nitrici  is  that, 
"when  agitated  with  twice  its  volume  of  concentrated  solution* 
of  muriate  of  lime  (chloride  of  calcium)  12  per  cent,  of  ether 
slowly  separates."  Now  as  the  proportion  of  ether  added  to  the 
spirit  was  20  per  cent.,  it  is  evident  that  8  per  cent,  is  held  in 
solution  by  the  mixture  of  spirit  and  chloride  of  calcium.  The 
last  Dublin  Pharmacopoeia  contained  a  process  of  a  similar  kind; 
that  is,  forming  a  nitrous  ether  by  the  action  of  nitric  acid  on 
spirit,  purifying  the  product  by  ammonia,  and  mixing  it  with 
10*5  volumes  of  rectified  spirit,  or  with  more  than  2*5  times  the 
quantity  used  by  the  Edinburgh  College,  making  the  product,  of 
course,  less  than  half  the  strength  as  regards  the  ether. 
*  This  should  be  "  saturated,"  as  otherwise  the  test  is  most  uncertain. 
This  can  only  be  ensured  by  always  having  undissolved  crystals  present 
in  the  solution  employed,  the  point  of  saturation  varying  much  with  tem- 
perature. 
