— 16 — 



Attention is directed to wnat t^econies ot tnem. Ceriam ones ai-^appear 

 quickly, others remain longer, or may be on the glass several days. 



Small vessels with glycerine, water, and alcohol may be kept open, 

 and results looked for. To show that when a substance disappears that 

 it is still in existence, place a few drops of ether, alcohol, chloroform, 

 or gasoline in the bottom of a tumbler. Cover with a glass or card. 

 When all the liquid has disappeared, have the glass examined, then care- 

 fully with a match, or better, along splinter, light the contents, when it 

 will burn. Use only small vessels, as these vapors make explosive mix- 

 tures with air. In these small quantities, with wide-mouthed vessels, 

 such as tumblers, there is no danger. For obvious reasons, a light 

 should not be brought near open vessels containing these substances. 

 In each kind of liquid used, show that where evaporation takes place, 

 heat is used up. Do this by moistening the bulb of a thermometer with 

 the liquid, and seeing the mercury fall more rapidly, the faster the 

 evaporation. With ether a degree below freezing may be reached. 

 Use cotton saturated with the liquid on the bulb of the thermometer. 



OF SOLIDS. 



To show that a solid may evaporate: Place some gum camphor in a 

 corked jar that has been wiped clean. In a few days crystals of cam- 

 phor will be found on the upper parts of the jar. 



If a small bit of camphor be heated in the bottom of a test-tube, it 

 first melts, then passes into vapor, which soon forms into crystals on the 

 sides of the upper part of the tube. 



A solid crystal of iodine heated in the bottom of a test-tube passes 

 into a beautifully-colored vapor; this forms into crystals on the upper 

 part of the tube. This experiment is excellent in showing a solid pass- 

 ing immediately into a vapor, in giving a vapor which can be seen; and 

 in giving a vapor that is heavier than air. 



Of course other substances may be chosen rather than the ones men- 

 tioned above, and the greater the number, the better. All of the above 

 are inexpensive as but very small amounts are needed and only very 

 small amounts should be used. It is a good rule to follow in experi- 

 menting with substances to use only small amounts. In such a case the 

 experiment will be more likely to succeed and will be more neatly done. 



THE PHENOMENA OF BOILING WATER. 



For the observation of the phenomena, a glass flask which will allow 

 its contents to be seen, should be secured. Let each step be noted; the 

 currents formed in the heated water, just how they go; the formation of 

 the bubbles-of air, which is simply the expanding of air dissolved in the 

 water (not steam); finally, the formation of bubbles of steam. These 

 form on the bottom of the vessel, just over the heating flame. The 

 first steam-bubbles do not reach the surface, since they condense on 



