Am.  Jour.  Pharm  ) 
July,  1877.  / 
Spirit  of  Nitrous  Ether. 
369 
since  the  process  can  be  of  value,  and  is  likely  to  be  applied  generally 
only,  if  it  can  be  conducted  with  ordinary  skill  and  care,  it  seemed 
desirable  to  determine  in  what  respect  fractional  dilutions  of  the  solu- 
tion, beyond  those  likely  to  occur  from  the  causes  named,  would 
influence  the  test.  Accordingly,  separate  portions  of  "concentrated 
spirit"  were  agitated  with  solution  of  chloride  of  calcium,  which  had 
been  diluted  with  different  proportions  of  water,  the  results  being 
shown  in  the  following  table  : 
Quantity  of  sat. 
sol.  CaCl.  used, 
cc. 
Quantity  of  water 
added, 
cc. 
Quantity  of  con- 
centrated spirit 
used, 
cc. 
Volume  of  crude 
ether  separated. 
cc. 
Percentage  of 
crude  ether 
indicated. 
20'0 
IO  O 
0-85 
i6'5 
i7'5 
2*5 
IO'O 
0.90 
17-0 
15:0 
5'° 
IO'O 
°'9S 
17*5 
IO'O 
IO'O 
IO'O 
1-05 
i8'5 
It  will  be  observed  that  a  dilution  of  the  saturated  solution  of  chlo- 
ride of  calcium  has  the  effect  of  increasing  the  quantity  of  crude  ether 
separated,  an  effect  which,  while  not  anticipated,  is  easily  accounted 
for  by  the  sparing  solubility  of  nitrous  ether  in  water.  It  is  remark- 
able, also,  that  the  increase  in  the  quantity  of  ether  separated  is  in 
direct  and  regular  proportion  to  the  degree  of  dilution,  being  0*5  per 
cent,  for  each  12*5  per  cent,  of  water  introduced.  When  we  take  into 
consideration,  however,  that  an  error  of  0*5  per  cent,  in  a  concen- 
trated spirit  of  the  above  strength  would  be  reduced  to  an  error  of 
0*117  per  cent,  for  the  finished  spirit,  we  may  safely  conclude  that  the 
trifling  quantity  of  water  introduced  by  a  possible  variation  in  the 
chloride  of  calcium  prepared  with  ordinary  care,  cannot  in  any  way 
affect  the  test. 
In  reply  to  the  fourth  question  I  would  therefore  say  : 
1.  The  method  of  the  "British  Pharmacopoeia"  for  determining  the 
strength  of  its  spirit  of  nitrous  ether  is  correct  and  reliable,  if  by  the  per- 
centage of  nitrous  ether  indicated  such  tc  crude  ether"  is  understood  as  will 
separate  upon  the  application  of  the  test. 
2.  The  test  is  not  materially  affected  by  a  slight  variation  in  the  strength 
of  the  saturated  solution  of  chloride  of  calcium  so  called ;  but  if  the  solution 
