166  Color  Requirements  of  US.P.  {AmXp?u'i9iuam' 
soda  solution,  and  taking  the  average  of  the  quoted  wholesale  prices 
for  these  substances,  the  cost  of  even  20  Gm.  of  such  available 
chlorine  need  not  exceed  this  amount,  thus  actually  making  the 
permanganate  method  even  slightly  cheaper  than  the  present  U.S. P. 
method,  even  if  we  do  not  consider  its  other  advantages.  It  appears 
therefore  that  from  whatever  standpoint  we  may  view  the  case  the 
present  U.S. P.  method  for  the  preparation  of  chlorinated  soda 
solution  is  certainly  not  as  advantageous  as  the  method  proposed 
as  a  substitute. 
Hygienic  Laboratory,  P.H.  and  M.H.S., 
Washington,  D.  C. 
A  ^JOTE  ON  CERTAIN  COLOR  REQUIREMENTS  OF  THE 
U.  S.  PHARMACOPOEIA. 
By  Norman  Roberts,  M.D., 
Hygienic  Laboratory,  U.  S.  Public  Health  and  Marine-Hospital  Service, 
Washington,  D.  C. 
Horace  North,  in  Lehn  and  Fink's  "  Notes-  on  New  Remedies  " 
for  January,  1910,  objects  to  the  U.S. P.  requirement  as  to  the 
color  of  turpentine,  in  that  there  is  no  such  thing  as  an  absolutely 
colorless  liquid,  not  even  distilled  water.  This  objection  is  valid, 
and  to  meet  it  definite  color-limits  should  be  officially  set.  The 
mdst  practicable  color  standards  would  probably  be  dilute  solutions 
of  stable  and  easily  obtainable  substances,  the  comparisons  being- 
made  in  large  colorless  glass  bottles  or  in  Nessler  tubes — not  in 
test-tubes,  since  in  a  tube  a  flat  bottom  is  necessary  to  avoid  irregular 
dispersion  and  consequent  inequality  of  the  light. 
Thus,  in  the  case  of  Oleum  Terebinthinse,  the  first  requirement 
should  read  somewhat  as  follows : 
"A  thin  liquid,  having  a  characteristic  odor;  color  not  more 
intense  than  that  of  a  1  :  (x)  solution  of  (potassium  dichromate)  in 
distilled  water,  when  viewed  by  diffused  daylight  transmitted  from 
below,  the  bodies  of  liquid  compared  being  one  decimetre  in  depth 
and  contained  in  similar  Nessler  cylinders  30  mm.  or  more  in 
diameter." 
Other  liquids  in  the  U.  S.  Pharmocopceia  having  the  same  vague 
