'^^jlr'^isss™''}        Organic  Matter  in  Potable  Waters.  45 
60  parts.  Since  the  citrate  only  serves  to  prepare  the  soluble  forms^ 
any  amount  of  iron  in  excess  is  immaterial. 
The  sodioferrous  citrate  is  prepared  by  adding  to  the  ferrous  citrate 
of  the  above  process  84  parts  of  hydrosodic  carbonate,  heating  until 
effervescence  ceases,  setting  the  solution  aside  till  the  carbonaceous 
residue  has  subsided,  decanting  the  clear  liquid,  evaporating  it  to  a 
syrupy  consistence,  and  spreading  it  on  glass  or  porcelain  plates  to  dry. 
A  definite  solution  can  also  be  kept  on  hand. 
The  sodioferrous  citrophosphate  is  prepared  by  adding  105  parts  of 
citric  acid  and  179  parts  of  sodic  phosphate  to  the  product  of  the  pre- 
ceding process,  and  proceeding  in  a  similar  manner  as  there  directed. 
The  ferroic  citrate  above  mentioned  is  a  very  useful  compound,  and 
could,  perhaps,  in  many  instances,  supplant  the  ferric  citrate.  Never- 
theless, a  complete  conversion  of  the  ferrous  into  ferric  citrate  would 
be  very  desirable.  At  one  time  the  writer  deemed  it  impossible  to  con- 
vert the  ferrous  citrate  by  means  of  nitric  acid,  but  recent  quite  suc- 
cessful trials  show  that  it  can  be  done.  If  45  parts  of  nitric  acid  is 
added  to  the  ferrous  citrate  above  obtained,  and  carefully  heated  to 
dryness,  perfect  transformation  is  effected. 
DETERMINATION  OF  ORGANIC  MATTER  IN  POTABLE 
WATER. 
By  J.  W.  Mallet. 
This  investigation  was  instituted  at  the  instance  of  the  American 
Government,  and  is  here  given  in  abstract :  the  full  report  has  not  yet 
been  pubhshed.  The  object  was  to  examine  the  chief  processes  em- 
ployed for  estimating  the  organic  matter,  to  test  the  absolute  and 
relative  accuracy  of  the  results  obtained  by  these  processes,  and  to 
ascertain  the  nature  and  scope  of  the  practical  conclusions  which  may 
be  secured.  The  processes  employed  were  the  "combustion,'^  "albu- 
minoid ammonia  and  the  "  permanganate,"  as  suggested  by  Forch- 
hammer,  but  in  the  form  advocated  by  Tidy.  The  waters  examined 
were  of  various  qualities,  good  and  contaminated  more  or  less,  and 
artificially-prepared  water  containing  animal  and  vegetable  matter. 
Each  analysis  was  made  in  triplicate,  and  the  first  portion  of  the 
report  gives  an  account  of  the  amount  of  concordance  observed 
between  the  analyses  of  each  sample  as  obtained  by  each  individual 
process.    In  the  combustion  process  there  was  found  an  average 
