Laboratory Manual of Elementary Chemical Physiology and Urine Analysis (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: Chapter II. CARBOHYDRATES. The name carboliydrate. as commonly used, is given to a peculiar group of bodies containing carbon, hydrogen and oxygen combined in certain proportions. In this group are included the sugars, the starches, the gums and some allied substances. The molecules of the compounds in this group contain, ordinarily, six, or some multiple of six, atoms of carbon with twice as much hydrogen as oxygen and usually enough to yield five or more molecules of water. In a strictly scientific classification certain molecules with five or even four atoms of carbon should probably be included among the carbohydrates. The carbohydrates are formed mainly in the vegetable kingdom and are, almost without exception, important food products. A few occur in the animal kingdom, but they are in this case derived from similar substances produced by plants. In the experimental study of these bodies it is best to begin with the starches, which are widely distributed in nature and important in the highest degree. Starch. Ex. 1. Prepare starch from the common potato as follows: Grate a potato to a pulp by means of an ordinary tin grater, mix the pulp with water and squeeze it through a piece of coarse unbleached muslin. Moisten the pulp again and repeat this operation several times, collecting the strained liquids in a large beaker. Allow the mixture to settle a half hour or longer and pour off the water, which contains some soluble albuminous substances, somecellular floating matter, but very little starch. Most of this will be found in the bottom of the beaker. Add some fresh water, stir up and allow to settle. Now pour the water off again and repeat these operations until the starch appears perfectly clean and white. Transfer this starch to a clean shallow dish and al...