To be of value, a disinfectant must touch all parts of- the object thought to be infected, so that no germ life may escape. All woodwork and walls where dust may collect and germs develop should be washed in an antiseptic solution and then in clear water and wiped dry. Sunshine is detrimental to growth of germ life, and hence is a fair antiseptic, but for hygienic cleanliness its work should be supplemented by use of antiseptic washes. All antiseptic or disinfectant solutions should be carefully la- belled poison and placed in a locked closet to prevent acci- dental poisoning. Method. — Outline. Materials. — Mouldy food, test-tubes, flour, sugar, alkalies, beef fat or olive oil, whiting, rotten stone, emery, benzine, kerosene. 60 HANDBOOK OF DOMESTIC SCIENCB A. Meaning of Cleanliness. Includes : — I. Removing dust. II. Preventing growth of germ life. III. Removing stains. B. How Accomplished. (a) Floating products in air allowed to settle and then removed by wiping surface with cloth dampened in water, soapy water, or mercuric chloride, water solution 1 : 40,000. Wash cloth, using hot soap-suds, and rinse in boiling water. Dry in sunshine. I, Prevent Entrance of Dust. Illustrate action of invisible life by showing mouldy bread or mouldy cheese. (a) To one tablespoon flour and one teaspoon sugar add three tablespoons boiling water✪ Mould Growth Experiment and cover the dish with a tightly fitting cover or one that projects over the edges. (6) In another dish left open place the same mixture. Leave both for several hours and examine. Explain the cause. Apply explanation to pro- duction of foul odors. II. Preventing Growth op Germ Life. Experiment 1. Action of Boiling Temperature. Prepare a weak cane suga,r solution, divide it, placing 1-|- teaspoonfuls in each of three test-tubes, (a) Boil solution and seal with cotton while hot. (h) Boil solution and leave exposed to air. (c) Seal solution 3 without first boiling. Leave the test-tubes (a) and (&) in dark place. Expose test-tube (c) to the direct sunshine. Examine for presence of moulds or bacterial life. THE KITCHEN (31 Experiment 2. Dampen flour and leave in dark place for several days. Let pupils draw conclusions as to the factors which aid growth of moulds and bacteria and how these conditions may be avoided. III. Removing Stains. (a) Grease stains. ' Kerosene, Gasolene, 1. Solvents,^ Benzine, Naphtha, Chloroform. 2. Soaps or emulsions. Explain nature of fats or oils and how alkalies may break up the combina- tion, forming a new compound called a soap. Experiment 3. Pour 1|- teaspoonf uls strong sodium hydroxid solution (ISTaOH) into an evaporating dish or a granite ware dish and add 3 c.c. warm tallow, fat, or olive oil. Boil the mixture, stirring till it becomes clear. Add tiny amount of salt✪ Soap Making Experiment (soap is not soluble in salt water). Soap should collect on top of the liquid. Use it in making soap-suds. Experiment 4. Prepare a greasy water ; add solution of sal soda (IS^aoCOa), or use ammonia or potassium carbonate to form an emulsion. [Wood ashes con- tain either potassium or sodium salts, depending upon the location of the vegetable growth. Inland woods are rich in potassium salts. Hence the use of wood ashes in removing grease stains.] (b) Stains on metals. (1) Why metals become discolored. Copper or brass oxidized by union with oxygen of air.

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To be of value, a disinfectant must touch all parts of- the object thought to be infected, so that no germ life may escape. All woodwork and walls where dust may collect and germs develop should be washed in an antiseptic solution and then in clear water and wiped dry. Sunshine is detrimental to growth of germ life, and hence is a fair antiseptic, but for hygienic cleanliness its work should be supplemented by use of antiseptic washes. All antiseptic or disinfectant solutions should be carefully la- belled poison and placed in a locked closet to prevent acci- dental poisoning. Method. — Outline. Materials. — Mouldy food, test-tubes, flour, sugar, alkalies, beef fat or olive oil, whiting, rotten stone, emery, benzine, kerosene. 60 HANDBOOK OF DOMESTIC SCIENCB A. Meaning of Cleanliness. Includes : — I. Removing dust. II. Preventing growth of germ life. III. Removing stains. B. How Accomplished. (a) Floating products in air allowed to settle and then removed by wiping surface with cloth dampened in water, soapy water, or mercuric chloride, water solution 1 : 40,000. Wash cloth, using hot soap-suds, and rinse in boiling water. Dry in sunshine. I, Prevent Entrance of Dust. Illustrate action of invisible life by showing mouldy bread or mouldy cheese. (a) To one tablespoon flour and one teaspoon sugar add three tablespoons boiling water and cover the dish with a tightly fitting cover or one that projects over the edges. (6) In another dish left open place the same mixture. Leave both for several hours and examine. Explain the cause. Apply explanation to pro- duction of foul odors. II. Preventing Growth op Germ Life. Experiment 1. Action of Boiling Temperature. Prepare a weak cane suga,r solution, divide it, placing 1-|- teaspoonfuls in each of three test-tubes, (a) Boil solution and seal with cotton while hot. (h) Boil solution and leave exposed to air. (c) Seal solution 3 without first boiling. Leave the test-tubes (a) and (&) in dark place. Expose test-tube (c) to the direct sunshine. Examine for presence of moulds or bacterial life. THE KITCHEN (31 Experiment 2. Dampen flour and leave in dark place for several days. Let pupils draw conclusions as to the factors which aid growth of moulds and bacteria and how these conditions may be avoided. III. Removing Stains. (a) Grease stains. ' Kerosene, Gasolene, 1. Solvents,^ Benzine, Naphtha, Chloroform. 2. Soaps or emulsions. Explain nature of fats or oils and how alkalies may break up the combina- tion, forming a new compound called a soap. Experiment 3. Pour 1|- teaspoonf uls strong sodium hydroxid solution (ISTaOH) into an evaporating dish or a granite ware dish and add 3 c.c. warm tallow, fat, or olive oil. Boil the mixture, stirring till it becomes clear. Add tiny amount of salt (soap is not soluble in salt water). Soap should collect on top of the liquid. Use it in making soap-suds. Experiment 4. Prepare a greasy water ; add solution of sal soda (IS^aoCOa), or use ammonia or potassium carbonate to form an emulsion. [Wood ashes con- tain either potassium or sodium salts, depending upon the location of the vegetable growth. Inland woods are rich in potassium salts. Hence the use of wood ashes in removing grease stains.] (b) Stains on metals. (1) Why metals become discolored. Copper or brass oxidized by union with oxygen of air.

Handbook of domestic science and household arts for use in elementary schools