THE ANALYST. MAY, 1902. ON THE INDIRECT ESTIMATION OF ALKALIES I N WATERS. BY W. W. FISHER, MA., F.I.C. (Read at t h Heeting, March 5, 1902.) IN the analysis of waters where mineral constituents have to be estimated, the more abundant bases determined are the lime, magnesia, and soda (inclusive of potash), and the acid radicles are usually chlorine, sulphuric acid, carbonic acids, and possibly nitric acid. After such determinations have been made, it becomes a somewhat tedious task to calculate the quantities of the compounds present, and much arith- metical work is involved in finding out whether the estimations duly balance each other. But this work of computation is greatly simplified if the relative molecular proportions of the several acids and bases are firat obtained by dividing the quanti-138 THE ANALYST.ties of each by their molecular weights, and taking the totals of acids and bases separately. If the work is absolutely correct, the totals will be alike, and they will be always near each other if the determinations are good; while any marked difference would indicate some analytical error, as only neutral compounds are present in the total solid residue. The following analysis will serve as an illustration : Total solids dried at 100" C. ... Total solids dried at 240" C. ... Soda, Na,O ... ... ... Magnesia, MgO ... ... ... Lime, CaO ... ... ... Total of bases ... Chlorine, C1, ... ... Sulphuric acid, SO, ... ... Carbonic acid, CO, ... ... Nitric acid, N,O, ... ... ... Grains per Molecular Molecular Gallon. Weights.Proportions. ... 243.00 ... 230.00 ... 53-14 -+ 62 0.8571 ... 11.99 2 40 0.299 ... 35.28 2 56 0.630 ... 100.41 1-7861 ... 18.00 -+ 71 0.2535 ... 103.88 + 80 1.2985 ... 9.55 f 44 0.2170 ... 0.84 + 108 0.0077 Total of acids ... Deduct oxygen = C1, ... 132.27 1.7767 ... 4.07 Total of salts ... Silica, etc. (difference) 128.20 .. 228.58 .. 1.42 Total solids ... ... The subsequent work of combining ... 230.00 the acids and bases, apportioning to each its due quantity, becomes very simple when the molecular proportions are employed, as 0.2535 molecules of chlorine will require 0,2535 molecules of sodium to form sodium chloride, no correction for the equivalent oxygen being required ; and after the nitric acid the remaining soda-viz., 0,5959-will neutralize an equal number of snlphuric acid molecules, and so on till all the salts are obtained.Molecules. (2) NaCl ... ... 0.2535 x 117 = 29-66 (2) NeNO, ... ... 0.0077 x 170 = 1.31 Na,SO, ... ... 0.5959 x 142 = 84.62 %SO, CaSO, CaCO, ... ... 0.2264 x 100 = 22.64 ... ... 0.299 x 120 = 35.88 . I . ... 0.4036 x 136 = 54.89 Total of salts ... ... 229.00 The molecular proportions may also be used with signal advantage for the indirect valuation of alkalies. The direct estimation of soda in waters is a trouble- some and lengthy operation, and in technical analyses is frequently omitted. Yet a knowledge of the amount of alkali in waters is often very desirable in order to allow the amounts of the salts to be approximately stated. It is generally im-THE ANALYST. 139 practicable to arrive at the amount of alkali by deducting the other constituents from the total solid residue, because many residues rich in sulphates retain water in variable quantity according to the conditions of drying.But when the lime and magnesia are known, and also chlorine, sulphuric, and carbonic acids (and possibly nitric acid also), the difference between the molecular totals of acids and bases gives a close approximation to the amount of alkali. In the analysis quoted above the total acids being 1.7837 molecules the basee would be the same, from which, if we deduct 0-929 molecules of lime and mqpesia, the residue of 0.8547 is soda ,(inclusive, of course, of traces of potash). Further multiplying 0-8547 by 62, we get 52.99 grains per gallon, which is little below the actual determination. The result may be controlled by a direct estimation of the total bases ae sulphates. The following example shows how an indirect determination works out : W heatfield water. Total solids '79.24 at 100" C. At 140" 78.12. Grains per Molecular Gallon. Weights. c1 ... ... 9-70 + 71 ... ... 4.66 + 80 ... 21.56 + 44 so3 CO, Na,O by difference [40*12] +- 62 MgO ... ... 0-5 i 40 CaO ... .._ 1.4 + 56 Molecular Proportions. 0.1366 0.0582 0.4900 0-6848 [0.6473] 0.0125 0.0250 A- Molecules. Grains. (2) NaCl ... . . . 0.1366 x 117 = 15.98 Na,SO, ... . . . 0.0582 x 142 = 8.26 Na2C03 . . . . . 0.4525 x 106 = 47.96 MgCO, ... ... 0.0125 x 84= 1.05 CaCO, ... ... 0.025 x 100= 2.5 0.6848 Salts ... 75-75 SiO, ... 2-5 Fe,O, ... 0.84 79-09 -- Total salts . . . ... 75.75