626
oa CHEMICAL EDUCATION
JOURNAL
MAY,1927
AN ANALYSIS OF ANALYTICAL RESULTS
A n analysis of sodium chloride yielded the following results, inaccurate despite the fact that the constituents totaled 100.0 per cent. N a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38.8% Cl.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61.2% 100.0%
If we divide the percentage of each constituent by its equivalent weight we obtain the quotients 1.657 and 1.724, respectively. If we now divide the smaller of these numbers by the larger we obtain the value 97.8.5%. For this value the name "Dickinson Number" of the analysis is suggested and i t is upon the calculation of this number that the analysis of analytical results depends. The "Dickinson Number" is primarily intended for use in connection with the results of the analysis of a mixture of several salts. Let us consider a liter of a solution containing 1.000 g. each of sodium chloride, calcium chloride, calcium sulfate, and sodium sulfate. The tabulated results of the analysis of this solution are reported ionically in parts per million, although the method is equally applicable to any system of reporting results. Each result is divided by the corresponding equivalent weight. The numerical value for the sum of the quotients of the positive ions is equal to the numerical value for the sum of the quotients of the negative ions, showing that the amounts found of the positive ions are balanced by the amounts found of the negative ions. In other words, the "Dickinson Number" of this analysis is 100.0%. CALCULATION OP THE "DICKINSON NUMBER" OP AN ANALYSIS Eq. wt.
Pt%./(lO)n
CLSO,--
Quotient
Sums
717 654
+ +
23 20
= =
31.2 32.7 63.9 ---------
1247 1382
+ +
35.5 48
= =
35.1 28.8
Na+ Cat+
"Dickinson Number"
=
63.9
+ 63.9
=
100.0%
63.9
