required to precipitate the zinc as ZnNH_{4}PO_{4} and what weight of
precipitate would be obtained?

!Answers!: (a) 0.04% error; (b) 39.97 cc.; (c) 1.909 grams.

101. A sample of magnesium carbonate, contaminated with SiO_{2} as its
only impurity, weighs 0.5000 gram and loses 0.1000 gram on ignition.
What volume of disodium phosphate solution (containing 90 grams
Na_{2}HPO_{4}.12H_{2}O per liter) will be required to precipitate the
magnesium as magnesium ammonium phosphate?

!Answer!: 9.07 cc.

102. 2.62 cubic centimeters of nitric acid (sp. gr. 1.42 containing
69.80% HNO_{2} by weight) are required to just dissolve a sample
of brass containing 69.27% Cu; 0.05% Pb; 0.07% Fe; and 30.61% Zn.
Assuming the acid used as oxidizing agent was reduced to NO in every
case, calculate the weight of the brass and the cubic centimeters of
acid used as acid.

!Answer!: 0.992 gram; 1.97 cc.

103. One gram of a mixture of silver chloride and silver bromide is
found to contain 0.6635 gram of silver. What is the percentage of
bromine?

!Answer!: 21.30%.

104. A precipitate of silver chloride and silver bromide weighs 0.8132
gram. On heating in a current of chlorine, the silver bromide is
converted to silver chloride, and the mixture loses 0.1450 gram
in weight. Calculate the percentage of chlorine in the original
precipitate.

!Answer!: 6.13%.

105. A sample of feldspar weighing 1.000 gram is fused and the silica
determined. The weight of silica is 0.6460 gram. This is fused with 4
grams of sodium carbonate. How many grams of the carbonate actually
combined with the silica in fusion, and what was the loss in weight
due to carbon dioxide during the fusion?

!Answers!: 1.135 grams; 0.4715 gram.

106. A mixture of barium oxide and calcium oxide weighing 2.2120 grams
is transformed into mixed sulphates, weighing 5.023 grams. Calculate
the grams of calcium oxide and barium oxide in the mixture.

!Answers!: 1.824 grams CaO; 0.3877 gram BaO.

APPENDIX

ELECTROLYTIC DISSOCIATION THEORY

The following brief statements concerning the ionic theory and a few
of its applications are intended for reference in connection with the
explanations which are given in the Notes accompanying the various
procedures. The reader who desires a more extended discussion of the
fundamental theory and its uses is referred to such books as Talbot
and Blanchard's !Electrolytic Dissociation Theory! (Macmillan
Company), or Alexander Smith's