Ignite and weigh a clean platinum dish, and measure into it 100 cc. of
the thoroughly shaken sample. Evaporate to dryness on a water bath. Then
heat the dish in an oven at 103° C. or 180° C. for one hour. Cool in a
desiccator and weigh. The temperature of drying should be mentioned in
the report. The increase in weight gives the total solids or residue on
evaporation. If 100 cc. of the sample was taken this weight expressed in
milligrams and multiplied by 10 is equal to parts per million of residue
on evaporation. The residue from waters low in organic matter but
relatively high in iron may be used, as a matter of convenience, for the
determination of iron.