43Q 
Advances  in  Pharmacy. 
Am.  Jour.  Pharm. 
June,  19 18. 
sary  to  perform  many  analyses  of  products  of  assured  purity  so  as 
to  determine  the  maximum  limit  of  allowable  variation  of  certain 
constituents.  An  increase  of  a  very  small  per  cent,  in  excess  of 
water  in  a  canned  fruit  or  vegetable  means  more  profit  and  its 
detection  is  often  difficult  if  not  impossible. 
Test  for  Arsenic  in  Sodium  Sulphate. — The  author  claims 
that  when  this  salt  is  dissolved  in  distilled  water  and  a  turbid  solu- 
tion results,  it  indicates  the  presence  of  arsenic.  This  can  be  proven 
by  adding  5  grams  of  sulphuric  acid  and  the  same  quantity  of  me- 
tallic zinc  to  100  mils  of  distilled  water.  The  container  is  then 
capped  with  a  white  filter-paper  cap.  This  paper  should  be  about 
four  to  five  inches  in  diameter  and  moistened  with  a  1  per  cent, 
solution  of  mercuric  chloride  and  dried  before  used.  The  ends  of 
the  paper  are  turned  downward  over  the  neck  of  the  bottle  and  held 
firmly  in  place  in  a  manner  most  convenient  to  the  operator.  If,  at 
the  end  of  forty  or  fifty  minutes,  the  paper  still  remains  white,  the 
reagents  are  considered  pure.  About  25  grams  of  the  sodium  sul- 
phate are  put  in  the  bottle  and  is  shaken  until  the  salt  is  dissolved. 
If  arsenic  is  present  the  paper  will  turn  yellow  and  then  brown,  the 
intensity  of  the  color,  of  course,  being  proportional  to  the  amount  of 
arsenic  present.  This  production  of  color  is  caused  by  the  hydro- 
gen arsenide  formed  by  contact  with  the  nascent  hydrogen.  The 
investigator  states  that  this  test  will  be  found  of  service  in  detecting 
very  small  amounts  of  arsenic  in  various  drugs.  As  small  a  quan- 
tity as  one  hundredth  of  a  milligram  per  cent,  can  be  demonstrated. 
This  test  was  particularly  useful  in  detecting  arsenic  in  cream  of 
tartar.  (/.  de  Medecine  de  Bordeaux,  by  P.  Carlos,  vol.  14,  p.  88, 
through  Jour.  A.  M.  A.,  February  23,  1918.) 
Chemical  Tests  of  Drinking  Water. — The  writer  of  this 
article  is  of  the  opinion  that  the  determination  of  the  chloride  in  a 
drinking  water  is  a  safe  test  of  its  purity.  He  found  that  when  this 
test  was  negative,  the  bacteriologic  tests  were  always  negative,  too, 
and  vice  versa.  When  the  chemical  test  showed  that  the  water  was 
good,  the  bacteriologic  findings  never  showed  that  it  was  pal- 
pably bad.  He  always  found  the  sodium  chloride  content  between 
8  and  17  mg.  in  the  pure  waters,  while  15,  20  or  35  mg.  showed 
manifest  pollution.  The  author  of  this  paper  also  claims  that  it 
is  very  important  to  know  the  average  chloride  content  of  the  pure 
waters  in  the  region.    This  can  be  determined  in  a  few  hours  by 
