silver, sulphur forms with silver a grayish black compound-a sulphide of silver. All the silver sulphides are insoluble in water. Rub such tarnished articles, before washing, with common salt. By replacement, silver chloride, a white chemical salt, is formed, which is soluble in ammonia. If the article be not washed in ammonia it will soon turn dark again. With an old or deep stain of silver sulphide friction must be used. The analysis of many samples of silver polish, showed them to be made up of either precipitated chalk, diatomaceous earth or fine sand. In using them, it is necessary to be careful in regard to the fineness of material since a few coarse grains will scratch the coating of soft silver. In former times the housewife. bought a pound of whiting for fifteen cents, sifted it. through fine cloth, or, mixing it with water, floated off the finer portion, and obtained in this way, twelve ounces of the same material for three ounces of which the modern housewife pays twenty-five cents or even more, when she buys it "by the box." The whiting may be made into a paste with ammonia or alcohol, the article coated with this and left till the liquid has evaporated. Then the powder should be rubbed off with soft tissue paper or soft cotton cloth, and polished with chamois. The presence of water always favors chemical change. Therefore iron and steel rapidly oxidize in damp air or in the presence of moisture. All metallic articles may be protected from such action by a thin Silver Polish Whiting Protecting Metals oily coating. Iron and steel articles not in use may covered with a thin layer of vaseline. be Rust can be removed from iron or steel by kerosene if not too deep. The tarnish on brass or copper will dissolve in ammonia water, but the objects tarnish again more quickly than if polished by friction. CHEMISTRY OF THE HOUSEHOLD. PART II. Read Carefully. Place your name and address on the first sheet of the test. Use a light grade of paper and write on one side of the sheet only. Do not copy answers from the lesson paper. Use your own words, so that your instructor may know that you understand the subject. Read the lesson paper a number of times before attempting to answer the questions. I. Name all the substances you can think of which are not soluble in water and are soluble in naphtha or benzine. 2. Does sugar neutralize acid chemically? Why? 3. How is soap made? What is the difference between hard and soft soap? 4. What is "hard" water? How does it act with soap? How is it softened? 5. Explain how "bluing" may make white clothes yellow. 6. Why remove stains when fresh? Why before washing? 7. Why is there danger in using naphtha, benzine, and to some extent alcohol near a light? 8. How do cotton and woolen differ in the effect of acids and alkalies upon them? 9. What precautions must be taken in bleaching or removing stains with chloride of lime solution or with Javelle water? IO. 10. Give a good method of starching and ironing clothes. II. If possible, try to remove some stain by a method given in this lesson and tell of the results. 12. Describe a good method of washing woolens. 13. Why does the drying of a little acid or alkali on a fabric have a very disastrous effect? 14. What is your method of washing dishes? 15. What can you say of acids, alkalies, salts? 16. What is "washing soda?" How should it be used? When should it not be used? 17. Why does strong soap or washing soda harm varnish or paint? 18. What is the cause of tarnish on metals? How can it be removed and prevented? 19. What advantages has ammonia for use in the laundry? 20. Do you understand everything given in this lesson paper? Are there any questions you would like to have answered? NOTE. After completing the test sign your full name. CHEMISTRY OF THE HOUSEHOLD. A Day's Chemistry. PART III. CHEMISTRY OF BAKING POWDER We will suppose that after the strenuous course of cooking, washing, and cleaning outlined for the morning, that the housekeeper still has strength to make soda biscuits for tea, and we will study the chemical action involved. One of the first chemical methods of securing carbon dioxide to use in making bread rise, was by putting hydrochloric acid and cooking soda together in a dough which might be put into the oven before the gas escaped from it. Cooking soda is a salt called bi-carbonate of sodium. It differs from the ordinary mono-carbonate of soda (washing soda) in yielding twice as much carbon dioxide in proportion to the sodium part of the compound. The saleratus of our grandmother's time was bi-carbonate of potash, made from wood ashes. The name is still used, but at all stores, cooking soda would be delivered invariably if saleratus were asked for. The true saleratus costs ten times as much as the soda and is no more effective. The carbonic acid is easily set free by chemical compounds of an acid nature, and new chemical compounds result. Cooking |