366  Abstracts  of  Theses  on  Chemical  Subjects.  {Ami.^usri,Pi9o^m 
These  precipitates  were  filtered  off  and  tested  ;  all  contained 
silica  except  II  and  none  contained  calcium.  Another  solution  was 
made  of  V  and  was  allowed  to  stand  without  previous  filtration. 
In  seven  days  considerable  precipitate  had  formed,  which  responded 
to  tests  for  silica,  but  not  for  calcium. 
The  author  concludes  that  silica  causes  the  difficulty  in  filtration 
in  proportion  to  the  amount  present,  all  those  solutions  which  were 
difficult  to  filter  giving  a  subsequent  precipitate  of  silica.  This 
subsequent  precipitation  is  due  to  silica,  which  also  promotes  pre- 
cipitation of  magnesium  citrate. 
II  made  a  permanent  solution  because  it  contained  no  silica. 
IV  made  a  permanent  solution  because  the  silica  present  was  all 
filtered  out  owing  to  its  insoluble  condition. 
Syrupus  Acidi  Hydriodici. — By  P.  S.  Lane.  Eight  samples  assayed 
by  the  U.S. P.  method  gave  percentages  of  HI  ranging  from  -44  to 
ri8,  average  -91. 
Three  gave  decided  tests  and  five  slight  tests  for  H3P02.  None 
contained  free  iodine,  although  one  had  a  reddish-brown  color. 
One  contained  considerable  glycerin. 
Acidity,  determined  by  titrating  with  sodium  hydrate  V.S.  and 
calculating  to  HI,  gave  higher  results  (due  to  presence  of  tartaric 
acid,  acid  potassium  tartrate  and  hypophosphorous  acid)  in  every 
case  except  one ;  in  this  case  the  higher  result  by  the  U.S.P.  assay 
was  due  to  the  presence  of  potassium  iodide. 
Difficulty  was  experienced  in  determining  the  end  reaction  on 
account  of  the  reducing  action  of  H3P02  upon  AgNOs,  causing 
blackening  of  the  solution.  The  reduced  silver  may  be  removed 
by  filtration,  but  in  any  case  high  results  are  obtained  owing  to 
reduction  of  a  portion  of  the  AgN03. 
Assay  of  Benzaldehyde. — By  E.  S.  Wright.  Difficulty  was  expe- 
rienced in  determining  the  exact  end  reaction  and  in  obtaining  con- 
cordant results  in  the  assay  of  benzaldehyde.  Three  assays  of  the 
same  sample  by  the  official  process  resulted  in  79-423,  78-023  and 
77*382  per  cent. 
Rosolic  acid  was  tried  as  indicator,  but  proved  unsatisfactory. 
The  official  assay  was  modified  to  the  extent  of  heating  the  benz- 
aldehyde,^kerosene  and  sodium  sulphite  together  in  a  glass-stop- 
pered bottle  to  6o°  C,  cooling  and  then  titrating.  Results  on  seven 
assays  of  the  same  sample  ranged  from  80-33  to  86-916  per  cent., 
average  83-96. 
