ed cubic centimeters of this filtrate require 29.62 cc. of 0.1062
N hydrochloric acid for neutralization, using phenolphthalein as an
indicator. Calculate percentage of NaOH, Na_{2}CO_{3}, and H_{2}O.

!Answers!: 78.63% NaOH; 4.45% Na_{2}CO_{3}; 16.92% H_{2}O.

40. A sodium hydroxide solution (made from solid NaOH which has been
exposed to the air) was titrated against a standard acid using methyl
orange as an indicator, and was found to be exactly 0.1 N. This
solution was used in the analysis of a material sold at 2 cents per
pound per cent of an acid constituent A, and always mixed so that
it was supposed to contain 15% of A, on the basis of the analyst's
report. Owing to the carelessness of the analyst's assistant, the
sodium hydroxide solution was used with phenolphthalein as an
indicator in cold solution in making the analyses. The concern
manufacturing this material sells 600 tons per year, and when the
mistake was discovered it was estimated that at the end of a year
the error in the use of indicators would either cost them or their
customers $6000. Who would lose and why? Assuming the impure NaOH used
originally in making the titrating solution consisted of NaOH and
Na_{2}CO_{3} only, what per cent of each was present?

!Answers!: Customer lost; 3.94% Na_{2}CO_{3}; 96.06% NaOH.

41. In the standardization of a K_{2}Cr_{2}O_{7} solution against iron
wire, 99.85% pure, 42.42 cc. of the solution were added. The weight of
the wire used was 0.22 gram. 3.27 cc. of a ferrous sulphate solution
having a normal value as a reducing agent of 0.1011 were added
to complete the titration. Calculate the normal value of the
K_{2}Cr_{2}O_{7}.

!Answer!: 0.1006 N.

42. What weight of iron ore containing 56.2% Fe should be taken to
standardize an approximately 0.1 N oxidizing solution, if not more
than 47 cc. are to be used?

!Answer!: 0.4667 gram.

43. One tenth gram of iron wire, 99.78% pure, is dissolved in
hydrochloric acid and the iron oxidized completely with bromine water.
How many grams of stannous chloride are there in a liter of solution
if it requires 9.47 cc. to just reduce the iron in the above? What
is the normal value of the stannous chloride solution as a reducing
agent?

!Answer!: 17.92 grams; 0.1888 N.

44. One gram of an oxide of iron is fused with potassium acid sulphate
and the fusion dissolved in acid. The iron is reduced with stannous
chloride, mercuric chloride is added, and the iron titrated wi