« AnteriorContinuar »
(e) oxalic acid, () sulphuretted hydrogen, (g) manganese chloride.
987. How is manganese dioxide recovered, by Weldon's process, from manganese chloride ?
988. When the higher oxides of manganese are heated in a current of hydrogen, what body remains, and what are its properties?
989 2:6789 grammes of an oxide of manganese when heated till constant in hydrogen left a residue which weighed 2-4907 grammes. Find the composition of the oxide.
990. Give three distinct methods for ascertaining the quantity of Mno, in a sample of commercial manganes dioxide. Describe the advantages of each method.
991. Oʻ139 gramme of pyrolusite when treated with hydrochloric acid yielded enough chlorine to liberate 0-336 gramme iodine from potassium iodide. Find the percentage of MnO, in the pyrolusite.
992. Represent by equations the action of sulphuric acid, and of sulphuric acid in presence of potassium oxalate on manganese dioxide.
993. What happens when (a) manganese chloride and (6) manganese dioxide are strongly heated in air ?
994. How is potassium manganese alum prepared ? Give the proportions of each constituent required.
995. In an analysis of pyrolusite by Fresenius' method, the following results were obtained :
2'2711 grammes of the oxide yielded 17091 gramme carbon dioxide. Find the percentage of Mno, in the oxide.
996. 0°7804 gramme of a hydrated oxide of manganese left, when heated in hydrogen, 0.5674 gramme residue. Find the percentage of manganese and the formula of the hydrate.
997. What weight of manganese dioxide when heated should yield 2476 litres of oxygen at 14° C., and 754 m.m. pressure?
998. What is chrome iron ore, and how is it treated so as to prepare potassium chromate ?
999. Describe the preparation of the chlorides and oxides of chromium, and state from which the metal may be most easily obtained.
1000. How may potassium bichromate be converted into the chromate and vice verså ?
1001. Give equations for the reactions which occur when each of the following bodies is added to solution of potassium bichromate—a) silver nitrate, (6) sulphuric acid, (c) potash, (d) sulphuretted hydrogen, (e) sulphur dioxide.
1002. What is the formula for chrome alum? Give two distinct methods for preparing it.
1003. What occurs when the bichromate of potassium and the bichromate of ammonium are separately heated ?
1004. What is chlorochromic acid, and how is it prepared ? What is its action on water? Express the reactions by equations.
1005. Compare the analogous compounds of chromium and sulphur, and name any chromium compounds which are isomorphous with the corresponding sulphur ones.
1006. What happens when a solution of chromic acid is treated with zinc ?
1007. How much oxygen by weight and volume should be evolved by heating 2'98 grammes of potassium bichromate with sulphuric acid, and how much chlorine should be evolved on treating the same quantity with hydrochloric acid ?
1008. What is the composition of the crystalline substance formed by treating potassium bichromate with strong hydrochloric acid ?
1009. What are the most characteristic tests for the compounds of chromium ?
1010. Write a list of the most abundant compounds of iron found naturally, and state which are used as sources of the nietal.
1011. In what bodies is iron found native ? How could you ascertain whether a body contained native or combined iron ?
1012. How is chemically pure iron obtained, and what are its properties?
1013. Describe processes for the assay of iron ores : (a) by the dry method, (6) by means of potassium permanganate.
1014. State briefly how the complete quantitative analysis of an iron ore is made, indicating particularly how the quantities of sulphur, manganese, phosphorus, silica, and iron are ascertained.
1015. Describe how malleable iron is obtained by each of the following processes—(a) by the Catalan forge, (6) by Siemens' process.
1016. How is cast-iron made? Sketch an ordinary blast-furnace, and explain fully how it is used.