60 INJURY BY SMELTER WASTES. 
When the salts are obtained in a hydrochloric-acid solution, ready for the determina- 
tion of calcium, magnesium, and sodium, pass through hydrogen sulphid to get rid of 
copper. Filter, evaporate to dryness, again take up in hydrochloric acid, and deter- 
mine calcium, magnesium, and sodium in aliquots of this solution. 
Black alkali. 
Solutions required: (1) A standard N/50 sodium-carbonate solution. (2) A standard 
N/50 sulphuric acid solution. (3) A solution of erythrosin containing 0.25 gram to a 
liter of water. (4) Chloroform. 
Meruop: Transfer 200 cc of the soil extract, obtained as in the preceding method, 
to a platinum dish, add 50 to 150 cc of standard sodium carbonate according to the 
amount of soluble salts of calcium and magnesium present, and evaporate to dryness. 
Rub the residue up with distilled carbon-dioxid-free water, transfer to a 100 cc gradu- 
ated flask, make up to the mark, shake thoroughly, stopper, and allow to stand until 
clear. When clear, carefully remove 50 cc without disturbing the residue in the 
bottom of the flask and transfer to the titrating bottle. For this purpose use a bottle 
of the best colorless glass without any tinge of pink, with ground-glass stopper and of 
about 250 ce capacity. Add 5 cc of chloroform and 1 cc of erythrosin and titrate the 
solution with the standard acid until the color disappears. The solution should be 
vigorously shaken after each addition of acid, the chloroform producing a milky 
appearance, which makes the reading of the end point sharp and certain. 
If less sulphuric acid is required than that necessary to balance one-half of the 
sodium carbonate added, it is evident that some of the sodium carbonate has been 
used up and that the solution originally contained no black alkali. If, on the other 
hand, more sulphuric acid is required than that equivalent to one-half of the sodium 
carbonate added, then black alkali was originally present and can be calculated from 
the amount of standard sulphuric acid used in excess of that necessary to neutralize 
one-half the sodium carbonate originally added. 
WATERS. 
Total copper. 
Shake sample thoroughly till well mixed with sediment and use 500 cc for analysis. 
Evaporate to dryness in a porcelain dish and determine total copper by the same 
methods used for total copper in soils. 
Soluble copper. 
Filter off 1,000 to 2,000 ce of the water from its sediment. Evaporate to dryness, 
take up with 1 or 2 cc of nitric acid by the aid of heat, dilute, filter, and determine 
soluble copper by the method used for soluble copper in soils. 
Soluble salts. 
Filter off 1,000 to 2,000 cc of the water from its sediment and determine carbonates, 
bicarbonates, chlorids, sulphates, calcium, magnesium, and sodium according to the 
methods given for these constituents in waters in Bulletin 91, Bureau of Chemistry, 
U.S. Department of Agriculture. 
aSkinner, J. Amer. Chem. Soc., 1906, 28: 77. 
