72 OUR BODIES AND HOW WE LIVE 



The carbohydrates are burnt up in the body, and set 

 free a considerable amount of energy. The energy called 

 for in muscular work and that which is transformed into 

 bodily heat come largely from their oxidation. 



Experiment 23. To test for starch. The test for starch is a very 

 weak solution of iodine, the addition of which to starch will result 

 in a blue color. Pour a tablespoonful of the starchy water obtained 

 from Experiment 21 into a test tube and boil. The starch dissolves 

 and the solution becomes translucent. If a drop or two of very weak 

 solution of iodine be added to the cold starch solution, a blue color 

 will result. 1 



Experiment 24. Secure a specimen of the various kinds of flour 

 and meal, peas, beans, farina, sago, cornstarch, rice, and tapioca. 

 Boil a small quantity of each in a test tube for some minutes. Put 

 a bit of each thus cooked on a white plate and test for starch by 

 adding two or three drops of very weak solution of iodine. Note the 

 various changes of color, blue, greenish, orange, or yellowish. 



Experiment 25. To test for sugar. The test for sugar is Fehling's 

 solution (easily obtained of the druggist in the form of solution or in 

 tablets). The little white grains found in raisins are grape sugar 

 or glucose. Milk sugar is readily bought of the druggist. Dissolve 

 one quarter of a teaspoonful of grape or milk sugar in a test tube 

 one quarter full of water. Add an equal amount of Fehling's solution 

 and bring the mixture to a boil. Note that an orange or brick-red 

 precipitate settles to the bottom of the tube. 2 



103. Fats and Oils. The chief fats and oils used as food 

 are those of meat, eggs, butter, and milk, also the various 



1 The tincture of iodine cannot be diluted -with water, but it can be 

 diluted with a saturated solution of potassium iodide. A few crystals of 

 iodine may be dissolved in a saturated solution of potassium iodide to make 

 an amber-colored or pale brown solution. 



2 Fehling's solution does not keep well. Make a fresh solution shortly 

 before it is to be used. Before using, test it by boiling a small quantity in 

 a clean test tube. If it does not keep its clean blue color, a fresh supply 

 should be prepared before making any tests. 



