In all cases the results are calculated in milligrams per I liter, no matter how many liters were taken and parts per 100,000 or grains per gallon recorded as the last step after using the tables. THE USE OF THE CURVES. In using the curves * the weights in milligrams per liter found are taken as abscissæ, and the points of intersection on the various curves are noted. The corresponding intersections on the curves of the substances which are to be reported are observed on the horizontal lines. From these intersections the values of abscissæ are again taken, which are the results required. Where there is an excess of elements or groups of opposite character the lines are drawn to the values of ordinates. For instance, 20 mg. of Cl equivalent are subtracted from the 30 mg. found by analysis, and the amount combined is taken on the line of ordinates. The corresponding intersection on the NaCl or KC1 curve is then noted, and the amount of the compound recorded. The excess is counted from zero to the line of ordinates, where it is compared with the next strongest basic radical. The alkalies when weighed as chlorides or sulphates need not be put in terms of the oxides as a step. Both table and curves are only carried out to three places, as that is as great a degree of accuracy as is requisite in water analysis. In applying the curves for boiler compounds, the amount of soda ash, caustic soda and lime are calculated for each separate corrosive or scale-forming substance and then added, or one corrective may be calculated for certain constituents and another for others. Attention is hereby called to the fact that less quantities of correctives than calculated are often found sufficient. *The author expects to have plates published giving all the calculations for calculating water analysis, etc. |