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ON  IODO  SULPHATE  OF  QUININE. 
ON  THE  OPTICAL  PROPERTIES  OF  THE  IODO-SULPHATE  OF 
QUININE  AND  DISULPHATE  OF  QUINIDIN,  AND  ON  THEIR 
APPLICATION  IN  DETECTING  THESE  SUBSTANCES  IN  THE 
URINE  OF  PATIENTS  UNDER  TREATMENT  WITH  THESE  ALKA- 
LOIDS. 
By  William  Bird  Herapath,  M.  D,,  of  Bristol,  England. 
The  observations  of  the  author  are  contained  in  three  papers 
published  in  the  Pharmaceutical  Journal,  vol.  xi.  448  and  499, 
and  in  vol.  xiii.  page  216.  We  have  already  (vol.  xxv.  page  136 
of  this  Journal,)  published  a  brief  statement  in  relation  to  the 
iodo-sulphate.  The  original  papers  are  numerously  illustrated 
with  wood  cuts,  exhibiting  the  crystalline  forms  of  the  iodo-sul- 
phate, and  the  various  appearances  they  assume  under  the  influ- 
ence of  polarized  light.  Dr.  Herapath,  presuming  that  many 
readers  would  not  appreciate  some  of  his  statements,  has  very  pro- 
perly prefaced  his  remarks  with  a  short  account  of  the  manner  of 
observing  and  applying  the  phenomena  of  polarized  light,  which 
we  give  entire. 
"  Philosophers  have  been  acquainted,  since  the  time  of  Malus, 
with  several  methods  of  polarizing  a  beam  of  ordinary  light,  the 
principal  of  which  may  be  arranged  under  two  heads. 
1st.  Polarization  by  reflection  ;  as  from  the  surfaces  of  glass, 
china,  water,  resin,  and  other  polished  substances  not  possessing 
metallic  properties. 
2d.  Polarization  by  transmission,  as 
a.  By  double  refraction,  as  by  carbonate  of  lime. 
b.  By  absorption,  as  tourmaline. 
c.  By  dispersion,  as  by  agate,  &c. 
The  words  polarization  of  light  may,  perhaps,  require  some 
explanation  ;  it  is  that  faculty  which  certain  bodies  possess  of  so 
altering  a  beam  of  ordinary  white  light  incident  upon  them  that 
it  is  no  longer  capable  of  being  transmitted  by  certain  other 
transparent  substances  at  certain  angles  or  in  certain  positions, 
so  that  under  the  requisite  conditions  these  crystalline  diaphanous 
bodies  become  as  if  opaque  to  this  polarized  light. 
The  doubly  refractive  power  of  carbonate  of  lime  has  been 
generally  made  use  of  for  the  study  of  these  phenomena,  and 
