74 
Seidlitz  Powders. 
( Am.  Jour.  Pharm. 
I    February,  1902. 
Chemical  considerations  require  so  much  time  for  their  descrip- 
tion that  I  shall  simply  be  content  with  naming  over  such  processes 
as  have  been  found  most  satisfactory  at  the  Testing  Station,  Phila- 
delphia. For  this  information  I  am  indebted  to  Dr.  George  E. 
Thomas,  the  chemist  in  charge  of  this  branch  of  the  work. 
For  Color,  Hazen's  Platinum  Cobalt  Standard,  described  by  Leff- 
man. 
For  Turbidity,  Whipple  and  Jackson,  Mt.  Prospect  Laboratory, 
Brooklyn. 
For  Solids,  100  c.c,  evaporate  to  dryness,  with  loss  on  ignition. 
Suspended  matter,  collected  on  filter  of  asbestos,  operating  with  a 
litre  of  water. 
The  two  ammonias  collect  six  tubes  from  each  distillate  for 
Kesslerization.  The  peculiar  clouding  of  the  distillate  noticed  at 
times  on  addition  of  Nessler  Solution  may  be  corrected  by  addition 
-of  mercuric  chloride  to  Nessler  Solution. 
Nitrites. — Alpha  naphthylamine  hydrochloride  and  sulphanilic 
acid. 
Nitrates. — Reduction  by  aluminum  foil  and  direct  Nesslerization 
of  the  ammonia. 
Oxygen  Consumed. — Potassium  permanganate  and  oxalic  acid. 
I  c.c.  potassium  permanganate  sol.  =  -oooi  gm.  O. 
Chlorine. — Titrate  with  nitrate  silver,  potassium  bichromate  as 
indicator;  using  yellow  light  gives  sharper  indication  of  end  reaction. 
Alkalinity. — Hehner's  method,  using  J?    H2S04,  described  by 
Leffman. 
Total  hardness. — Soap  method. 
Oxygen  dissolved. — Winkler's  method  in  Sutton. 
N 
C02. — Seyler's  method  — —  Na2C03,   using  phenolphtalein  as 
an  indicator,  described  in  a  recent  issue  of  the  Journal  of  the  Amer- 
ican Chemical  Society. 
SEIDLITZ  POWDERS. 
By  Roland  H.  Frknch. 
This  paper  is  to  be  regarded  as  the  result  of  an  effort  on  the  part 
of  the  writer  to  simplify  the  seemingly  complicated  and  impracticable 
methods  which  have  been  set  forth  by  previous  investigators  of  the 
