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!Answer!: 20.08 cc. !Answer!: 5.70 cc. A sample of pyrolusite weighing 0.6000 gram is treated with 0.9000 gram of oxalic acid. What is the percentage of MnO , in the sample? !Answer!: 84.47%. A solution contains 50 grams of KHC O .H C O .2H O per liter. In the analysis of an iron ore containing 60% Fe O , a sample weighing 0.5000 gram is taken and the iron is reduced with sulphurous acid.
After washing it is transferred to the flasks of the apparatus mentioned in the first part of this paper, and estimated. Myself and several others have found this always to be a true MnO , and not a varying mixture of protosesquioxide and binoxide, and will thus yield accurate results.
A mixture of the chlorides of sodium and potassium from 0.5000 gram of a feldspar weighs 0.1500 gram, and after solution in water requires 22.71 cc. of 0.1012 N silver nitrate for the precipitation of the chloride ions. What are the percentages of Na O and K O in the feldspar? !Answer!: 8.24% Na O; 9.14% K O. How many grams of Mn O can be obtained from 1 gram of MnO ? !Answer!: 0.8774 gram.
Carbonic acid is evolved, and, passing into the adjoining flask, is absorbed by the baryta, precipitating it as carbonate. To prevent the precipitate forming around or choking up the entrance tube, the flask must be agitated at short intervals to break it off. The reaction so familiar to us in other determinations is expressed thus: MnO +KO,C O +2SO = MnO,SO +KO.SO +2CO ,
The reactions involved are: MnO + 4HCl > MnCl + 2H O + Cl Cl + 2KI > I + 2KCl I + 2Na S O > 2NaI + Na S O Assuming that the weight of thiosulphate corresponding to the volume of sodium thiosulphate solution used is known, what is the corresponding weight of manganese dioxide? From the reactions given above, the following proportions may be stated: 2Na S O :I = 316.4:253.9, I :Cl = 253.9:71,
For example, the amount of MnO in a sample of the mineral pyrolusite may be determined by dissolving the mineral in hydrochloric acid, absorbing the evolved chlorine in a solution of potassium iodide, and measuring the liberated iodine by titration with a standard solution of sodium thiosulphate.
Cl :MnO = 71:86.9. After canceling the common factors, there remains 2Na S O :MnO = 316.4:86.9, and the factor for the conversion of thiosulphate into an equivalent of manganese dioxide is 86.9/316.4.
It is then titrated back with decinormal soda; from this is now readily deducted the amount of carbonic acid, and from that the MnO , holding in view that 44 parts of carbonic acid is equivalent to 43.5 of MnO or 98.87 per cent, and that 1 c.c. of the N/10 baryta solution is equivalent to 0.0022 grm. of CO .
If the pyrolusite under examination is known to be of high grade, say 80 per cent pure, or above the calculation of the oxalic acid needed may be based upon an assumption that the mineral is all MnO . If the quality of the mineral is unknown, it is better to weigh out three portions instead of two and to add to one of these the amount of oxalic prescribed, assuming complete purity of the mineral.
Pyrolusite, when pure, consists of manganese dioxide. Its value as an oxidizing agent, and for the production of chlorine, depends upon the percentage of MnO in the sample.
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