Ami«g°«st  iP884rm'}    Reducing  Action  of  Vaseline  and  Paraffin.  437 
washed,  and  the  whole  made  up  to  500  cc.  Two  series  of  estimations 
were  made  on  50  cc.  and  100  cc.  each  of  the  solution.  The  following 
are  the  numbers  obtained : 
(a)  50  cc  required  6*7  ce.  oxalic  solution  to  complete  decolorization. 
(5)  50  cc.  required  6*6  cc.  oxalic  solution  to  complete  decolorization. 
(e)  100  cc.  required  13'7  cc.  oxalic  solution  to  complete  decolorization. 
(d)  100  cc.  required  13*6  cc.  oxalic  solution  to  complete  decolorization. 
Mean  =  13'53  cc.  of  volumetric  solution  of  oxalic  acid  required  to  decolor" 
ize  100  cc.  of  permanganate  solution. 
Then  13*53  cc.  X  "00314  =  -04248  K2Mn2Og  (found)  =  53-1  per  cent. 
The  filtration  through  glass-wool  did  not  entirely  free  the  liquid 
from  suspended  manganic  oxide.  This  interfered  slightly  with  the  accu- 
racy of  the  readings.  It  is  noteworthy  that  the  absence  of  the  resinous 
coating  increases  the  percentage  of  unreduced  permanganate  from  30 
to  53-1. 
Estimation  of  Pills  containing  Silver  Nitrate. — These  pills,  when 
examined,  had  been  made  eighty-five  days.  Two  strengths  were  esti- 
mated (No.  1)  containing  2  grains,  and  (No.  2)  J  grain  each  respectively 
of  the  salt.  Both  were  made  up  to  a  total  weight  of  5  grains  each  by 
Mr.  Martindale's  excipient.    They  were  not  coated. 
One  gram  of  No.  1  (representing  *4  gram  of  silver  nitrate)  was  care- 
fully broken  down  under  distilled  water  at  the  ordinary  laboratory 
temperature  (about  20°C),  by  means  of  a  glass  rod.  The  silver  nitrate 
entered  readily  into  solution.  The  total  liquid  collected  was  allowed 
to  settle,  then  filtered  through  glass-wool,  the  residue  and  wool  being 
washed  till  free  from  traces  of  silver  salt,  and  the  solution  made  up  to 
500  cc.  Some  finely  divided  kaolin  still  remained  suspended  in  the 
liquid.  This  prevented  an  accurate  gravimetric1,  determination.  Instead, 
two  series  of  separate  volumetric  estimations  were  made  on  50  cc.  and 
150  cc.  respectively,  using  a  solution  of  amnionic  thiocyanate  (of  which 
1  cc.  had  been  ascertained  to  equal  '0171  gram  of  commercial  crystals 
of  silver  nitrate)  with  iron  alum  as  indicator.  The  following  are  the 
numbers  obtained  : 
(a)  50  cc.  silver  solution  required  2-4  cc.  NH4CNS  solution. 
(6)  50  cc.  silver  solution  required  2*35  cc.  NH4CNS  solution. 
(e)  150  cc.  silver  solution  required  7*1  cc.  NH4CNkS  solution. 
(d)  150  cc.  silver  solution  required  7'05  cc.  NH.tCNS  solution. 
Mean  =  4-725  cc.  NH4CNS  solution  required  to  completely  precipitate 
100  cc.  of  silver  nitrate  solution. 
Then  4'725  X  '0171  =  -08079  AgN03  (found)  =  100-99  per  cent. 
