of the MoO_{3} to Mo_{24}O_{37}), requires 100 cc. of normal
KMnO_{4} to oxidize it back to MoO_{3}, what is the percentage of
P_{2}O_{5}?

!Answer!: 33.81%.

59. In the analysis of a sample of steel weighing 1.881 grams the
phosphorus was precipitated with ammonium molybdate and the yellow
precipitate was dissolved, reduced and titrated with KMnO_{4}. If the
sample contained 0.025 per cent P and 6.01 cc. of KMnO_{4} were used,
to what oxide was the molybdenum reduced? 1 cc. KMnO_{4} = 0.007188
gram Na_{2}C_{2}O_{4}.

!Answer!: Mo_{4}O_{5}.

60. What is the value of 1 cc. of an iodine solution (1 cc. equivalent
to 0.0300 gram Na_{2}S_{2}O_{3}) in terms of As_{2}O_{3}?

!Answer!: 0.009385 gram.

61. 48 cc. of a solution of sodium thiosulphate are required to
titrate the iodine liberated from an excess of potassium iodide
solution by 0.3000 gram of pure KIO_{3}. (KIO_{3} + 5KI + 3H_{2}SO_{4}
= 3K_{2}SO_{4} + 3I_{2} + 3H_{2}O.) What is the normal strength of the
sodium thiosulphate and the value of 1 cc. of it in terms of iodine?

!Answers!: 0.1753 N; 0.02224 gram.

62. One thousand cubic centimeters of 0.1079 N sodium thiosulphate
solution is allowed to stand. One per cent by weight of the
thiosulphate is decomposed by the carbonic acid present in the
solution. To what volume must the solution be diluted to make it
exactly 0.1 N as a reducing agent? (Na_{2}S_{2}O_{3} + 2H_{2}CO_{3} =
H_{2}SO_{3} + 2NaHCO_{3} + S.)

!Answer!: 1090 cc.

63. An analyzed sample of stibnite containing 70.05% Sb is given for
analysis. A student titrates it with a solution of iodine of which 1
cc. is equivalent to 0.004950 gram of As_{2}O_{3}. Due to an error on
his part in standardization, the student's analysis shows the sample
to contain 70.32% Sb. Calculate the true normal value of the iodine
solution, and the percentage error in the analysis.

!Answers!: 0.1000 N; 0.39%.

64. A sample of pyrolusite weighing 0.5000 gram is treated with an
excess of hydrochloric acid, the liberated chlorine is passed into
potassium iodide and the liberated iodine is titrated with sodium
thiosulphate solution (49.66 grams of pure Na_{2}S_{2}O_{3}.5H_{2}O
per liter). If 38.72 cc. are required, what volume of 0.25 normal
permanganate solution will be required in an indirect determination
in which a similar sample is reduced with 0.9012 gram
H_{2}C_{2}O_{4}.2H_{2}O and the excess oxalic acid titrated?

!Answer!: 26.22 cc.

65. In the determina