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1. Some metals, active enough to combine extensively with carbon, may be produced by the reduction of the oxides with aluminium. 2. To make a precipitation as complete as possible it is necessary to add a slight excess of one of the ions concerned in the formation of the precipitate. 3. The particles in the positive rays are assumed to be formed by removal of one or more electrons from the atoms. 4. Chlorine reacts with calcium hydroxide to form a mixed salt with the two negative ions. 5. In a number of instances some ions are hydrolyzed. 6. In a number of instances some ions are hydrolyzed to give acidic solution. 7. Atoms are too small to be seen even under a powerful microscope. 8. The metal hydroxides react with acids and with oxides of non-metals to form water and a class of compounds known as salts. 9. Carbon dioxide reacts with sodium hydroxide to yield water and sodium carbonate. 10. To be useful as an ore, an iron mineral must contain at least 30 to 40 per cent of iron. 11. To improve the quality of pig-iron it is to be purified by melting in a furnace. 12. Ammonium ions interact with water to form hydronium ions in equilibrium with molecular ammonia. 13. To determine the relative weights of different elements we were to use the relative system of atomic weights. 14. In order to liquefy a gas at a temperature below its critical temperature it is practically necessary only to compress the gas.