!Answers!: 13.22% MgO; 40.54% CaO. 92. The calcium in a sample of dolomite weighing 0.9380 gram is precipitated as calcium oxalate and ignited to calcium oxide. What volume of gas, measured over water at 20°C. and 765 mm. pressure, is given off during ignition, if the resulting oxide weighs 0.2606 gram? (G.M.V. = 22.4 liters; V.P. water at 20°C. = 17.4 mm.)
!Answer!: 227 cc.
93. A limestone is found to contain 93.05% CaCO_{3}, and 5.16 % MgCO_{3}. Calculate the weight of CaO obtainable from 3 tons of the limestone, assuming complete conversion to oxide. What weight of Mg_{2}P_{2}O_{7} could be obtained from a 3-gram sample of the limestone?
!Answers!: 1.565 tons; 0.2044 gram.
94. A sample of dolomite is analyzed for calcium by precipitating as the oxalate and igniting the precipitate. The ignited product is assumed to be CaO and the analyst reports 29.50% Ca in the sample. Owing to insufficient ignition, the product actually contained 8% of its weight of CaCO_{3}. What is the correct percentage of calcium in the sample, and what is the percentage error?
!Answers!: 28.46%; 3.65% error.
95. What weight of impure calcite (CaCO_{3}) should be taken for analysis so that the volume in cubic centimeters of CO_{2} obtained by treating with acid, measured dry at 18°C. and 763 mm., shall equal the percentage of CaO in the sample?
!Answer!: 0.2359 gram.
96. How many cubic centimeters of HNO_{3} (sp. gr. 1.13 containing 21.0% HNO_{3} by weight) are required to dissolve 5 grams of brass, containing 0.61% Pb, 24.39% Zn, and 75% Cu, assuming reduction of the nitric acid to NO by each constituent? What fraction of this volume of acid is used for oxidation?
!Answers!: 55.06 cc.; 25%.