^\iti'mi^^'}  Preparation  of  Diluted  Phosphoric  Acid.  465 
limited  ranges,  but  move  at  rates  corresponding  with  all  refrangibili- 
ties,  having  simply  an  excess  of  the  higher  ones,  though  the  same 
substance  in  the  solid  state  may  act  quite  differently,  as  in  the  case  of 
nitrate  of  uranium,  and  possibly  the  fluorescent  material  in  the  as- 
phalt, which  may  be  related  to  the  solid  hydrocarbon  fluorescing 
green,  which  Becquerel  mentions  {La  Lumiere,  tome  i,  p.  382). 
In  this  general  connection  let  me  mention  that  I  have  observed  that 
while  the  acid  salts  of  quinine  generally  are  fluorescent,  the  chloride 
is  not,  and  that  hydrochloric  acid  will  decompose  the  acid  sulphate  so 
as  to  destroy  its  fluorescence. 
There  are  several  other  points  in  connection  with  this  and  the  fore- 
going subject,  which  I  must  leave  for  a  subsequent  discussion. 
July,  1871. 
P.  S. — Aug.  1st.  I  have  just  obtained  results  with  turmeric,  which 
seem  to  indicate  that  its  fluorescence  is  due  to  the  presence  of  a  sub- 
stance not  yet  observed,  soluble  in  water,  and  without  any  color. — 
Amer.  Journ.  of  Science  and  ArU^  Sept.^  1871.  ' 
PREPARATION  OF  DILUTED  PHOSPHORIC  ACID. 
By  E.  B.  Shuttleworth. 
The  officinal  process  of  the  British  pharmacopoeia  for  diluted  phos- 
phoric acid  is  a  troublesome  and  dangerous  one.  The  use  of  closed 
glass  vessels,  when  operating  on  an  explosive  substance  like  phos- 
phorus, is  attended  with  considerable  risk,  not  only  to  the  apparatus, 
but  the  person  and  property  of  the  operator.  The  .apparatus  is  un- 
necessarily complicated,  involving  the  employment  of  a  retort  and  Lie- 
big's  condenser,  while  the  advantage  gained  on  the  score  of  economy 
of  acid  is  so  trivial  as  to  be  practically  unworthy  of  consideration. 
A  much  better  process  is  that  of  the  United  States  Pharmacopoeia. 
In  this  the  diluted  nitric  acid  is  placed  in  a  porcelain  capsule ;  the 
phosphorus  is  added  and  the  whole  covered  by  an  inverted  glass  fun- 
nel, of  such  dimensions  that  its  rim  rests  on  the  inside  of  the  capsule, 
near  the  surface  of  the  liquid.  A  gentle  heat  is  applied,  and  if  ne- 
cessary, the  action  moderated  by  the  addition  of  a  little  distilled 
water,  which  can  be  readily  applied  without  in  any  way  disturbing 
the  operation.  After  the  phosphorus  has  disappeared,  the  funnel'^'is 
removed,  and  the  concentration  of  the  acid  is  effected  in  the  same 
vessel,  by  a  further  application  of  heat. 
30 
