SOAP BUBBLE BALLOON. 



261 



Fig. 114. Balloon with one Bubble 

 blown inside another. 



ascending power becomes considerably weakened or even entirely 

 lost. 



Caution. In carrying out this experiment care must be taken 

 not to allow the bubble filled with 

 coal gas to come in contact with 

 a chandelier or sunburner, &c., 

 otherwise a slight explosion may 

 be caused by the firing of the gas, 

 and glass shades may be thus 

 broken ; the bubbles at the ceil- 

 ing may be fired without any 

 danger by means of a long taper 

 tied to a stick, provided they are 

 nowhere near to curtains, hang- 

 ings, or other inflammable objects. 



Expt. 308. Buoyant Bubble 

 inside a Heavier one. Blow a 

 bubble with air and fix it on the 

 ring as in the last experiment. 

 Now dip the blowing tube again in the soap solution, and by a 

 quick motion pass the blowing tube through the top of the first 

 bubble, as in Expt. 306, and connect the blowing tube with the 

 bladder of coal gas. You will now be able to blow one bubble 

 within another, the innermost containing coal gas and the outer- 

 most air. The ascensional power of the innermost one will be 

 sufficient (if the ring is not too heavy) to lift up both, the outer 

 one with the car attached being lifted up by the lighter internal 

 bubble (fig. 114). If the car be held by the thread and the 

 outer bubble broken by touching 

 with a dry stick, &c., the ring and 

 car will drop on account of the 

 buoyancy being no longer exerted 

 upon it, whilst the inside bubble 

 will escape and rapidly rise to the 

 ceiling. The outer bubble in this 

 case is comparable with the netting 

 thrown over the covering of the 

 ordinary balloon, from which netting 

 the car is actually suspended. 



Expt. 309. Illustration of Den- 



Sity Of Carbon Dioxide. Get a 



large basin or small tub and strew 



powdered chalk or whiting over the bottom inside ; now pour on 



a tumblerful of strong vinegar, or some diluted hydrochloric acid ; 



^ 115> Soap Bubble floating in 



Tub half-filled with a heavy 

 Gas - 



