APPENDIX 323 



tube under water. Observe what happens, and ask for an oral ex- 

 planation. 



EXP. 4. If a test-tube is only partially filled with water, closed 

 and inverted with its mouth under water, hydrogen being then 

 introduced, a mixture will be formed of the air left in the tube, 

 with the volume of hydrogen represented by the quantity of water 

 originally placed in the tube. Fill four test-tubes one-quarter, one- 

 third, one-half, and two-thirds, respectively, full of water; invert 

 in pneumatic trough, displace the water with hydrogen; close with 

 thumb, carry to flame and compare violence of explosions. 



EXP. 5. Dry the end of the delivery-tube with a bit of filter- 

 paper. Allow the gas to flow upon bits of moist litmus paper, red 

 and blue : note whether their color is affected. 



EXP. 6. Wipe a beaker clean and dry; then hold it for a min- 

 ute or more over the mouth of the delivery-tube and note whether 

 anything is deposited upon the beaker. Light the hydrogen as it 

 issues from the tube, and again hold the beaker over the jet. 



EXP. 7. Fill a small bottle with hydrogen over the pneu- 

 matic trough. Lifting the bottle, mouth down, out of the trough 

 with your left hand, push a lighted match well up into it, holding 

 the match by means of the steel forceps, with your right hand. 



EXP. 9. Disconnect the generating apparatus, and filter its 

 liquid contents into an evaporating dish, being careful not to fill 

 the latter above the lip; the superfluous liquid may be thrown away 

 and any undissolved zinc can be left in the generator, for future 

 use. The small stove in the draught-closet is lighted, the porcelain 

 dish set upon it and heated with a small flame until the liquid has 

 all evaporated. As this operation takes some time, and requires 

 little attention, it can be conducted during the progress of some 

 of the succeeding experiments. 



Write the equation which expresses the action of hydrochloric acid upon zinc. 



OXYGEN 



EXP. 10. Heat about one gram of potassium chlorate in a 

 clean, dry test-tube, being careful not to allow the flame at any time 

 to strike that portion of the tube which is above the substance, since 



