300 
SPIRITUS  2ETHERIS  NITRICI. 
that  given,  the  boiling  point  of  the  mixture  is  higher,  and  the  re- 
actions occurring  at  a  higher  temperature  produce  more  aldehyd 
in  the  distillate,  and  are  less  easily  and  less  economically  con- 
trolled.   When  a  much  larger  proportion  of  alcohol  is  used,  it 
distils  off  before  the  proper  reactions  take  place,  the  distillation 
of  unchanged  alcohol  frequently  continuing  till  the  proportion 
is  considerably  less  than  that  adopted  in  the  formula,  and  the 
reaction  when  it  does  occur  is  of  course  correspondingly  more 
active.    The  manner  in  which  nitric  acid  and  alcohol  are  mixed 
has  a  most  interesting  and  important  bearing  upon  the  character 
of  the  reactions,  as  well  as  upon  the  period  and  rate  at  which 
these  reactions  occur.    Thus  the  acid,  if  new  and  colorless,  may 
be  so  slowly  and  carefully  mixed  with  the  alcohol  that  in  the  pro- 
portions given  in  the  London  officinal  formula  the  whole  of  the 
prescribed  distillate  may  be  drawn  over  before  any  appreciable 
reaction  occurs.    In  practice,  upon  a  scale  of  2|  gallons  of 
materials,  this  has  twice  occurred  to  me,  without  any  particular 
care,  or  premeditated  slowness  in  mixing.    On  the  other  hand  if 
alcohol  is  slowly  poured  into  nitric  acid,  a  most  violent  reaction 
occurs  before  the  proportions  become  equal,  and  this  violent  re- 
action continues  long  after  the  proportions  pass  the  limit  of  5  to 
1,  or  until  the  cold  alcohol  quenches  the  reaction  altogether. 
Such  a  mixture  has  the  sensible  properties  of  spirit  of  nitre.  At 
some  period,  and  in  some  portions  of  all  mixtures  as  ordinarily 
made,  some  of  these  conditions  of  concentration  are  liable  to 
occur,  and  thence  to  act  as  a  starting  point  from  whence  general 
reaction  may  commence  earlier  or  later,  as  the  case  may  be. 
Hence  the  utility  of  a  proper  proportion,  and  of  a  temperature 
regulated  at  the  lowest  point  of  equable  reaction,  as  the  best,  the 
safest,  and  the  most  economical  means  of  controlling  such  varia- 
tions in  the  reactions.    The  means  of  controlling  within  narrow 
practical  limits,  the  strength  of  the  preparation  by  the  proposed 
formula  is  very  satisfactory,  and  not  difficult  to  accomplish.  It 
consists  simply  in  taking  the  specific  gravity  of  that  portion  of 
the  distillate  in  the  rectification,  which  comes  over  below  the 
boiling  point  of  alcohol,  which  portion  will  contain  nearly  all  the 
ether,  and  may  for  practical  purposes  be  considered  as  a  solution 
of  hyponitrous  ether  in  a  small  proportion  of  alcohol.  The 
operator  will  then  have  three  specific  gravities,  namely  of  the 
