6 
The  Purification  of  Benzin. 
Am.  Jour.  Pharm. 
Jan.,  1890. 
chloride,  but  if  well  diluted  first  changes  only  into  ferric  salicylate. 
Sodium  benzoate  solution  is  decomposed  by  acids  to  yield  the  sparingly 
soluble  benzoic  acid. 
Mercuric  chloride  is  decomposed  by  solution  of  potassium  arsenite, 
but  if  the  alkaline  solution  has  first  added  to  it,  in  slight  excess, 
diluted  hydrochloric  acid  no  precipitation  will  take  place  on  the  addi- 
tion of  the  mercurial  salt;  pyrophosphate  and  phosphate  of  iron  solu- 
tions precipitate  with  dilute  phosphoric  acid.  The  National  Formu- 
lary recommends  the  usage  of  dilute  metaphosphoric  acid,  in  place  of 
the  officinal  "ortho"  variety,  as  yielding  a  permanently  clear  solution. 
In  conclusion,  the  writer  would  say  that  in  these  "notes"  presented 
he  has  endeavored  to  give,  not  an  exhaustive  list  of  special  incompat- 
ibles,  but  simply  a  general  expression  of  those  liable  to  occur  in  the 
every-day  routine  of  prescription  work. 
What  to  do  with  an  incompatible  prescription  is  a  question  for  indi- 
vidual judgment  and  cannot  here  be  entered  into.  The  usual  practice, 
in  the  event  that  the  prescription  involves  no  serious  change,  is  to 
accept  the  situation  and  dispense  as  written.  On  the  other  hand, 
where  some  serious  change  is  liable  to  take  place,  it  is  almost  super- 
fluous to  state  that  it  is  the  duty  of  the  pharmacist  to  consult  the 
physician  before  dispensing. 
THE  PURIFICATION  OF  BENZIN  FOR  PHARMACEU- 
TICAL AND  CHEMICAL  PURPOSES. 
By  George  M.  Berixger,  Ph.  G. 
Read  at  the  Pharmaceutical  Meeting  December  17, 1889. 
The  U.  S.  Pharmacopoeia  of  1880  introduced  benzin,  describing  it 
as  a  purified  distillate  from  American  petroleum,  consisting  of  hydro- 
carbons chiefly  of  the  marsh  gas  series  and  homologous  compounds, 
having  a  sp.  gr.  from  0*670  to  0*675  and  boiling  at  50°  to  60°  C.  (122° 
to  140°F.).  It  is  required  to  be  free  from  heavy  hydrocarbons,  pyro- 
genous  products  and  sulphur  compounds. 
The  British  Pharmacopoeia  requires  a  boiling  point  of  50°  to  60°C. 
(122°  to  140°F.)}  but  allows  a  much  wider  range  of  gravity,  viz. : — 
0-670  to  0-700. 
The  German  Pharmacopoeia  describes  benzin  as  a  colorless  non- 
fluorescent  fractional  distillate  of  petroleum  of  the  sp.  gr.  0*640  toO*670,. 
distilling  over  almost  completely  between  55°  to  75°C. 
The  U.  S.  Pharmacopoeia,  by  limiting  the  product  to  a  sp.  gr.  of 
