78 DIRECTIONS FOR PERFORMING 



6. Fill a jar with hydrogen, and in a similar way dip the 

 gas downward and burn it over a lamp. This shows in a very 

 striking manner the difference between H and CO 3 in respect 

 to specific gravity. The one, we see, is dipped upward, the 

 other downward. 



7. Balance a large paper bag or box on a delicate pair of 

 scales, or in any simple manner one's ingenuity may suggest. 

 Empty into the box a large jar of CO 3 , and the box will quickly 

 descend. 



8. Arrange little wax-tapers in a wooden or pasteboard 

 trough, as on page 65. Light them, and then pour in at the 

 top a bottle of carbonic acid gas. If the proper slant is given 

 to the trough, all the candles will be extinguished. 



72. i. Olefiant gas may be made by heating in the flask one 

 part, by measure, of alcohol and two parts of sulphuric acid. 

 Pass it through a smution of potash, as shown on page 88, and 

 then collect in the gas-bag. Fit a piece of glass tubing, drawn 

 to a fine point at one end, to the stop-cock of the gas-bag by 

 means of a bit of the rubber tubing. On turning the stop- 

 cock and forcing out the gas it may be ignited, when it will 

 burn with a clear white light. 



2. Fill a tall jar one-third full of olefiant gas, and the re- 

 mainder with chlorine gas. On lighting, the mixture will 

 burn with a dense cloud of smoke. HC1 is the product of the 

 combustion. 



3. Mix with oxygen ana explode in soap-bubbles. It pro- 

 duces a greater noise even than the " mixed gases." Great 

 care must be taken not to let the light approach the gas-bag 

 containing the mixture. 



4. Fit a large test-tube with a cork and a piece of glass 

 tubing, drawn to a fine point at the outer end. Fill the tub 

 with fine dry pine-shavings. On heating, the gases from the 

 wood will pass off, and can be ignited at the jet- tube. The 

 test-tube can be held by a strip of twisted paper or wire. 



5. At the close of the ist exp. perform the one figured on 

 page 79. A small piece of wire-gauze, 4 or 6 inches square, 

 for this purpose can be purchased of any tinsmith. If you do 

 not force the gas out too rapidly, you will be able to burn it 

 on either side of the gauze at pleasure. 



