AmNov.r;SanL>'}  Revision  of  the  U.  S.  Pharmacopoeia.  521 
and  titrated  instead  of  taking  7  84  grm.  and  dissolving  and  using 
only  one-third  for  the  test  ? 
Ammonium  Nitrate  might  have  been  dropped,  as  its  use  is  almost 
entirely  restricted  to  dental  practice  for  preparing  nitrogen  monoxide 
and  even  here  the  purchase  of  the  compressed  gas  in  cylinders  is 
generally  deemed  preferable  to  preparing  the  same. 
In  assaying  Amyl  Nitrite,  a  control  experiment  should  be  directed, 
using  the  same  quantities  of  reagents  and  alcohol  and  under  the 
same  conditions  without  the  amyl  nitrite  and  the  volume  of  any  gas 
generated  deducted  from  that  found  in  the  assay. 
The  method  of  making  aromatic  waters  is  again  changed.  The 
cotton  method  of  1880  is  discarded,  and  in  place  of  magnesium  car- 
bonate as  a  distributing  material  for  the  essential  oil,  as  in  1870, 
calcium  phosphate  is  now  directed.  This  is  not  a  new  idea,  but  is 
one  which  I  have  frequently  employed  since  1878.  It  is  to  be 
remarked  that  as  magnesium  carbonate  is  very  much  more  bulky 
or  specifically  lighter  than  precipitated  calcium  phosphate  that  an 
increased  weight  of  the  latter  should  be  directed.  The  amount  now 
directed  is  nearly  the  same  weight  as  that  of  magnesium  carbonate 
formerly  ordered,  and  in  most  cases  it  will  be  found  advantageous 
to  increase  this  to  8  grm.  instead  of  4  grm.  in  the  official  formula. 
The  process  is  otherwise  unobjectionable,  provided  proper  care  is 
exercised  in  selecting  precipitated  calcium  phosphate  answering  the 
official  tests  for  purity.  Several  samples  examined  by  the  writer 
have  contained  notable  quantities  of  carbonate,  alkali  and  metallic 
impurities. 
Bitter  almond  water,  chloroform  water  and  creosote  water  are 
direct  solutions  in  water  without  the  aid  of  any  distributing  material 
or  chemical  means. 
Aqua  Hydrogenii  Dioxidi  is  the  official  name  for  solution  of 
hydrogen  peroxide,  and  an  extensive  formula  for  its  preparation 
from  barium  dioxide  and  phosphoric  acid  is  given,  the  strength 
adopted  being  10  volumes  of  available  oxygen  when  estimated  by 
the  process  of  assay  given.  This  preparation  and  likewise  chlorine 
water,  and  the  ammonia  waters  should  be  classified  with  liquors  or  a 
new  class  of  solutions.  In  addition  to  the  other  stringent  requirements 
for  Distilled  Water  it  must  now  be  free  from  carbonic  acid.  This  is 
a  degree  of  purity  we  fear  not  often  attained,  and  where  necessary 
it  is  easy  to  direct  boiling  to  dispel  the  carbon  dioxide. 
