xiv GENERAL INTRODUCTION 



then said to have neutralized each other, and the resulting 

 substance is called a salt. The salt may be obtained by 

 evaporating the water of the solution. Most common 

 minerals are salts. If the last experiment is tried with 

 soda and sour buttermilk, the demonstration will show 

 some of the facts involved in bread making with the use 

 of these substances. 



Test for Starch. — Starch turns blue with iodine. The 

 color may be driven away by heat, but will return again as 

 the temperature lowers. Procure a few cents' worth of tinc- 

 ture of iodine and dilute it. Get a half dozen pieces of 

 paper and cardboard, all different, and test each for starch 

 by placing it over mouth of bottle and tipping the bottle 

 up. If much starch is present the spot will be blue-black 

 or dark blue ; if little starch, pale blue ; if no starch, brown 

 or yellowish. 



Make pastes with wheat flour, potato starch, and corn 

 starch. Treat a little of each with a solution of rather 

 dilute tincture of iodine. Try grains from crushed rice 

 with the same solution. Are they the same color ? Cut 

 a thin section from a potato, treat with iodine and examine 

 under the microscope. 



To study Starch Grains. — Mount in cold water a few 

 grains of starch from each of the following : potato, wheat, 

 arrowroot (buy at drug store), rice, oats, corn. Study under 

 microscope the sizes, forms, layers, fissures, and location 

 of nuclei, and make a drawing of a few grains of each. 



Test for Grape Sugar. — Make a thick section of a bit of 

 the edible part of a pear and place it in a bath of Fehling's 

 solution. After a few moments boil the liquid containing 

 the section for one or two minutes. It will turn to an 

 orange color, showing a deposit of an oxid of copper and 

 perhaps a little copper in the metallic form. A thin sec- 



