The Pharmaceutical era . tionwhich representsthe reaction. If the zinc bepure the reaction will proceed slowly. To hasten theevolution of the gas add a few drops of a solution of cu-pric sulfate, which by the deposition of metallic copperupon the zinc in some obscure way aids the reaction. After all the air has been expelled from the apparatus,which will require a minute or so, if the flask is not alarge one, ignite the issuing stream of hydrogen. If a further supply of gas is required, it may be col-lected by placing the end of the delivery tube under avessel filled with water and inverted in
The Pharmaceutical era . tionwhich representsthe reaction. If the zinc bepure the reaction will proceed slowly. To hasten theevolution of the gas add a few drops of a solution of cu-pric sulfate, which by the deposition of metallic copperupon the zinc in some obscure way aids the reaction. After all the air has been expelled from the apparatus,which will require a minute or so, if the flask is not alarge one, ignite the issuing stream of hydrogen. If a further supply of gas is required, it may be col-lected by placing the end of the delivery tube under avessel filled with water and inverted in a pneumatictrough. 5. Instead of the flask, a test tube about twelve centi-meters long may be used to contain the zinc, water andacid. By bringing the mouth of the tube to a flame, theissuing gas will take fire and burn within the tube witha nearly colorless flame. An empty tube inverted overthe generator tube will become filled with the gas, butmixed with air. This mixture will ignite at a flame witha slight Fig. 17.—Students Hydrogen Generator. LECTURE 16. Pharmaceutical Physics. General Principles of Heat. Ancient and Modern Theories.—Heat was anciently thoughtto be a kind of matter wbieh was present in hot bodiesand which left them on cooling. Later, when it was ob-served that bodies neither gained weight in becomingheated nor lost weight in cooling, it was seen that heatcould not be a kind of matter, for all known kinds ofmatter possess weight. Still later, heat was thoughtto be a special kind of force or energy, but with thediscovery of the fact and the enunciation of the general law that all forms of energy are mutually convertibleone into another, this theory had also to be is now almost universally believed that the tempera-ture of any portion of matter depends upon the motionof its molecules, the more rapid their motion, the higherthe temperature, and conversely, or in other words, thatheat is the energy of molecular motion. This is com-m
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