1. Calculate from the following determinations the percentages of ferrous, ferric, and total iron in the sample of ore used.
1 gram of ore dissolved and titrated required 26.7 c.c. of bichromate of potassium solution.
1 gram of ore dissolved, reduced, and titrated required 43.5 c.c. of bichromate of potassium solution.
Standard = 1.014.
2. One gram of an ore contained 0.307 gram of ferrous iron and 0.655 gram of total iron. The iron existing as oxide, what are the percentages of ferrous oxide (FeO) and ferric oxide (Fe2O3) in the ore?
3. One gram of brown iron ore dissolved in hydrochloric acid required 59.2 c.c. of stannous chloride (standard = 0.930). Another gram dissolved in acid and titrated with "permanganate" required 8.2 c.c. (standard = 0.4951). Calculate the percentages of ferrous, ferric, and total iron.
4. Another gram of the same ore, roasted, dissolved and titrated with stannous chloride, required 63.5 c.c. To what extent does this result confirm the others?
5. Two grams of a metal were dissolved and diluted to 100 c.c. Five c.c. were taken for a colorimetric determination, and required 4.5 c.c. of the standard ferric chloride solution. What is the percentage of iron in the metal?
NICKEL.
Nickel and cobalt are closely related in their chemical properties, and may best be considered together. Nickel is the commoner of the two, and is met with in commerce alloyed with copper and zinc as German silver; as also in the coinage of the United States and on the Continent. It is used for plating polished iron and steel goods, forming a coating little liable to rust and taking a good polish. The ores of nickel are not very common. Kupfernickel and chloanthite are arsenides of nickel with, generally, more or less iron and cobalt. Noumeite and garnierite are hydrated silicates of nickel and magnesia. The chief sources of nickel are these silicates, which are found in large quantity in New Caledonia; and a pyrites found in Norway, containing three or four per cent. of the metal. In smaller quantities it is more widely distributed, being frequently met with in copper ores; consequently, commercial copper is rarely free from it.