. The animans and man; an elementary textbook of zoology and human physiology. over the pan of water. Partly fill the test tube with themixture of potassium chlorate and black oxide of manganese (equalparts). Fit the test tube with a tightly fitting cork and a bent glassdelivery rod. Before placing the delivery tube in the water move thealcohol flame along the test tube so as to drive out the air and warmthe tube, that no moisture may form on the tube and break the glass. Then heat the mixture gradually, beginning at the top and working HUMAN PHYSIOLOGY: INTRODUCTION 293 toward the bottom. Aft
. The animans and man; an elementary textbook of zoology and human physiology. over the pan of water. Partly fill the test tube with themixture of potassium chlorate and black oxide of manganese (equalparts). Fit the test tube with a tightly fitting cork and a bent glassdelivery rod. Before placing the delivery tube in the water move thealcohol flame along the test tube so as to drive out the air and warmthe tube, that no moisture may form on the tube and break the glass. Then heat the mixture gradually, beginning at the top and working HUMAN PHYSIOLOGY: INTRODUCTION 293 toward the bottom. After a few seconds gas will come off. The de-livery tube may then be placed under water beneath the opening ofthe jar, and soon the bubbles of oxygen coming off will displace thewater in the jar. Caution.—After collecting a jar of oxygen (or several jars) lift theend of the delivery tube out of the water before removing the lamp,otherwise the water will rush back into the delivery tube and crack it. Insert the live coal of a splinter into the jar. It will burst into FIG. 155. Apparatus for collecting oxygen. (After Jenkins and Kellogg.) Or heat the end of a piece of picture wire and insert the red-hot wire intothe oxygen. It will burn with a bright flame, thus showing again thatoxygen supports combustion. Other experiments with oxygen may be found in books on elementarychemistry. Properties of Carbon.—Carbon is the chief solid elementin wood, muscle, fat, sugar, starch, etc., in fact in everysubstance that is or has been living. For this reason, sub-stances containing carbon are called organic substances. Itis found in coal, showing that coal was once a living sub-stance. A special branch of chemistry, called OrganicChemistry, is devoted to the study of the carbon compounds. The black substance, or charcoal, left after the splinterwas burned is almost pure carbon. It is without taste orodor. When carbon is cold it has little affinity for otherelements. When it is heat
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