Amju0i"'iSLarm'}       Notes  011  Practical  Pharmacy.  3.5-1 
though  nitrous  acid  passes  into  nitric  acid  by  contact  with  water, 
this  reaction  does  not  occur  in  the  presence  of  an  excess  of  nitric 
acid.  Few  remedies  have  a  more  general  and  widespread  reputa- 
tion than  this ;  it  is  now  frequently  prescribed,  more  than  eighty 
years  after  its  virtues  were  originally  discovered." 
The  nitrous  acid  used  is  known  in  commerce  as  fuming  nitrous 
acid  or  fuming  nitric  acid.  It  is  really  nitric  acid  holding  in  solu- 
tion nitrous  acid  fumes,  which  latter  may  be  wholly  removed  by 
boiling,  or  largely  by  simple  and  continued  exposure  to  air  ;  so  that 
the  commercial  product  varies  considerably  in  strength  of  absolute 
nitrous  acid. 
Remington's  Pharmacy  (1885),  p.  1027,  specifies  nitrous  acid  in 
the  formula  for  this  mixture,  as  does  also  the  National  Dispensa- 
tory of  1884  (p.  75)  and  1894  (p.  76).  Hope's  Camphor  Mixture 
is  still  largely  used,  at  least  with  us,  in  summer  dysenteries,  and 
if  Mr.  Hope's  contention  as  to  the  necessity  of  using  only  nitrons 
acid,  never  nitric,  is  correct,  then  the  National  Formulary  decidedly 
errs  in  following  the  formula  of  Ellis  and  specifying  the  latter. 
The  objection  sometimes  raised  as  to  the  difficulty  of  securing 
good  fuming  nitrous  acid  can  be  met.  The  pharmacist  can  easily 
make  his  own  nitrous  acid,  extemporaneously,  from  sodium  nitrite 
and  nitric  acid,  using  quantities  sufficient  to  yield  the  amount  of 
acid  in  the  formula,  which  is  small.  Messrs.  Rosengarten  &  Sons 
state  that  sodium  nitrite  of  the  new  official  strength  (97-6  per  cent.) 
is  readily  obtainable. 
Medicated  Waters. — In  the  making  of  medicated  waters — save 
those  prepared  by  distillation  or  direct  solution — the  new  Pharma- 
copoeia directs  precipitated  calcium  phosphate  as  the  distributing 
medium  in  about  the  same  proportion  as  that  directed  for  magne- 
sium carbonate  in  the  1870  issue.  As  was  pointed  out  by  the 
writer  ten  years  ago  (A.  J.  P.,  1884,  P-  65),  in  advocating  the  use 
of  precipitated  calcium  phosphate  for  this  purpose,  it  is  essential, 
in  order  to  properly  distribute  the  oil,  that  the  lime  compound  be 
used  in  double  the  quantity  of  magnesium  carbonate  usually  em- 
ployed, on  account  of  its  much  less  bulk.  The  official  quantity  of 
the  lime  compound  should  be  8  gm.  to  the  1,000  cc.  of  the  medi- 
cated water,  and  not  4  gm.,  as  directed. 
It  is  best  to  add,  as  the  Pharmacopoeia  directs,  all  the  water  to 
the  admixed  lime  compound  and  oil  before  filtration.    The  practice 
