AmMJa°rch.f9Mrm'}      The  Technical  Analysis  of  Water.  123 
of  cubic  centimetres  required  multiplied  by  -8162  (500  X  '583  X 
•0028)  equals  grains  of  calcium  oxide  per  United  States  gallon. 
Magnesia. — To  the  filtrate  from  the  calcium  oxalate  add  ammonia 
and  solution  of  sodium  phosphate,  allow  to  stand  over  night.  The 
liquid  is  then  filtered,  the  precipitate  washed  with  ammonia  water, 
dried,  ignited  and  weighed,  which  is  magnesium  pyrophosphate. 
Milligrammes  of  residue  multiplied  by  -2916  equals  grains  per 
United  States  gallon. 
The  Sulphates. — 200  c.c.  of  the  filtered  sample  of  water  are  acidi- 
fied with  hydrochloric  acid  and  barium  chloride  added  until  it 
ceases  to  give  a  precipitate.  Allow  to  stand  over  night.  The  liquid 
is  then  filtered,  the  precipitate  washed,  ignited  and  weighed,  which 
is  barium  sulphate. 
Milligrammes  of  residue  multiplied  by  -2916  equals  grains  per 
United  States  gallon. 
Sodium  Chloride. — Titrate  100  c.c.  of  the  filtered  sample  of  water 
with  standard  silver  nitrate  solution,  using  potassium  chromate  as 
indicator.  The  number  of  cubic  centimetres  required  multiplied  by 
•68(1  c.c.  AgN03  equals -ooi  1674  X  1000  X  '583)  equals  grains 
of  sodium  chloride  per  United  States  gallon. 
Calcium  Carbonate,  Magnesium  Carbonate  and  Sodium  Carbonate 
Combined. — Titrate  200  c.c.  of  the  filtered  sample  of  water  with 
standard  decinormal  sulphuric  acid,  using  methyl  orange  as  indi- 
cator. The  number  of  cubic  centimetres  required  multiplied  by 
1-4575  (500  X  '583  X  '005)  equals  combined  calcium  carbonate, 
magnesium  carbonate  and  sodium  carbonate  expressed  in  grains  of 
calcium  carbonate  per  United  States  gallon. 
Free  Carbonic  Acid.— -1 00  c.c.  of  the  sample  of  water  are  taken,  to 
which  is  added  3  c.c.  of  a  solution  of  barium  chloride,  2  c.c.  of  a 
saturated  solution  of  ammonium  chloride,  and  95  c.c.  of  lime-water, 
the  strength  of  which  has  been  previously  ascertained.  This  is 
allowed  to  stand  over  night  in  a  flask,  the  1 00  c.c.  is  filtered,  titrated 
with  decinormal  hydrochloric  acid.  The  number  of  cubic  centi- 
metres so  found  must  be  deducted  from  the  quantity  required  for 
the  lime-water.  The  remainder  multiplied  by  2-565  (2000  X  '583 
X  *0022)  equals  grains  of  free  carbonic  acid  per  United  States 
gallon. 
The  Combination  of  the  Acids  and  Bases. — Different  chemists  have 
different  schemes  of  uniting  the  bases  and  acids,  which  should  not 
be.    The  most  rational  method  would  be  to  state  the  acids  and 
