CHAPTER VI. 
METHODS OF ANALYSIS, OF CALCULATION, AND OF 
STATING RESULTS. 
METHODS OF ANALYSIS. 
Total Solids.— This determination is made by evaporating 
from 100 cc. to 500 cc. of the water to dryness on a water-bath 
in a weighed platinum dish, and then heating the residue to 
130° C. in the air-bath. The presence of various hygroscopic 
salts may cause this result to be more or less dependent on the 
quickness with which the weight is made. The result is of 
special use as a ‘‘control’’ test, so this determination is never 
neglected. It is sometimes advisable, after weighing, to ignite 
the dried residue, so as to notice if an appreciable blackening 
takes place. This blackening would indicate the presence of 
large quanties of organic matter. 
Determination of Bases.—The analysis for those aces that are 
most abundant is made by using a fresh sample of water, from 
one to ten liters, dependent on the amount of total solids ob- 
tained above, acidulating it with hydrochloric acid, and evapora- 
ting to dryness on the water-bath. The evaporation may be 
hastened by boiling gently at first in a porcelain evaporating 
dish, and adding measured quantities of water from time to time, 
and completing the operation on the water-bath. The residue is 
either heated on the water-bath till every trace of odor of hydro- 
chloric acid is gone, or it is heated to 110° C. on a water-bath 
forsome time. After moistening the residue with hydrochloric 
acid and digesting, water is added, and the solution is filtered. 
It is of the utmost importance to note at this stage that in the 
presence of notable quantities of calcium sulfate, a single treat- 
ment in this way is not sufficient, but the residue should be 
boiled several times with dilute hydrochloric acid and water. 
(85) 
