46.  Determine the percentage of iron in a sample of limonite from the following data:  Sample = 0.5000 gram.  KMnO_{4} used = 50 cc. 1 cc.  KMnO_{4} = 0.005317 gram Fe.  FeSO_{4} used = 6 cc. 1 cc.  FeSO_{4} = 0.009200 gram FeO.

!Answer!:  44.60%.

47.  If 1 gram of a silicate yields 0.5000 gram of Fe_{2}O_{3} and Al_{2}O_{3} and the iron present requires 25 cc. of 0.2 N KMnO_{4}, calculate the percentage of FeO and Al_{2}O_{3} in the sample.

!Answer!:  35.89% FeO; 10.03% Al_{2}O_{3}.

48.  A sample of magnesia limestone has the following composition:  Silica, 3.00%; ferric oxide and alumina, 0.20%; calcium oxide, 33.10%; magnesium oxide, 20.70%; carbon dioxide, 43.00%.  In manufacturing lime from the above the carbon dioxide is reduced to 3.00%.  How many cubic centimeters of normal KMnO_{4} will be required to determine the calcium oxide volumetrically in a 1 gram sample of the lime?

!Answer!:  20.08 cc.

49.  If 100 cc. of potassium bichromate solution (10 gram K_{2}Cr_{2}O_{7} per liter), 5 cc. of 6 N sulphuric acid, and 75 cc. of ferrous sulphate solution (80 grams FeSO_{4}.7H_{2}O per liter) are mixed, and the resulting solution titrated with 0.2121 N KMnO_{4}, how many cubic centimeters of the KMnO_{4} solution will be required to oxidize the iron?

!Answer!:  5.70 cc.

50.  If a 0.5000 gram sample of limonite containing 59.50 per cent Fe_{2}O_{3} requires 40 cc. of KMnO_{4} to oxidize the iron, what is the value of 1 cc. of the permanganate in terms of (a) Fe, (b) H_{2}C_{2}O_{4}.2H_{2}O?

!Answers!:  (a) 0.005189 gram; (b) 0.005859 gram.

51.  A sample of pyrolusite weighing 0.6000 gram is treated with 0.9000 gram of oxalic acid.  The excess oxalic acid requires 23.95 cc. of permanganate (1 cc. = 0.03038 gram FeSO_{4}.7H_{2}O).  What is the percentage of MnO_{2}, in the sample?

!Answer!:  84.47%.

52.  A solution contains 50 grams of KHC_{2}O_{4}.H_{2}C_{2}O_{4}.2H_{2}O per liter.  What is the normal value of the solution (a) as an acid, and (b) as a reducing agent?

!Answers!:  (a) 0.5903 N; (b) 0.7872 N.

53.  In the analysis of an iron ore containing 60% Fe_{2}O_{3}, a sample weighing 0.5000 gram is taken and the iron is reduced with sulphurous acid.  On account of failure to boil out all the excess so_{2}, 38.60 cubic centimeters of 0.1 N KMnO_{4} were required to titrate the solution.  What was the error, percentage error, and what weight of sulphur dioxide was in the solution?

!Answers!:  (a) 1.60%; (b) 2.67%; (c) 0.00322 gram.

54.  From the following data, calculate the ratio of the nitric acid as an oxidizing agent to the tetroxalate solution as a reducing agent:  1 cc.  HNO_{3} = 1.246 cc.  NaOH solution; 1 cc.  NaOH = 1.743 cc.  KHC_{2}O_{4}.H_{2}C_{2}O_{4}.2H_{2}O solution; Normal value NaOH = 0.12.

!Answer!:  4.885.