152 



JUNIOR GRADE SCIENCE 



happens proceed to fill one or two jars. When the jars have been 

 filled, it is better not to remove them from the water until you want to use 

 them. Collect also a soda-water bottle half full of the gas. 



Caution. Be careful not to bring a light near the thistle funnel or tube 

 delivering the gas, even when thi action in the flask seems to have ceased, or a 

 dangerous explosion may occur. 



Be careful also that none of the acid used gets upon your fingers or clothing. 



ii. The liquid left in tne flask. Filter off the liquid in the flask from 



the undissolved zinc (sufficient zinc 

 should be used to leave a quantity 

 still undissolved : if all has dis- 

 appeared add more and wait till 

 the action ceases. Partially eva- 

 porate the liquid and allow it to 

 crystallise. A quantity of clear 

 colourless crystals is formed. 

 Examine the crystals and sketch 

 the most perfect. Heat some of 

 the crystals in a tube and observe 

 that they melt, give off water 

 (\vhich can be collected and 

 proved to be water), and leave a 

 white powder. 



iii. Hydrogen burns but extin- 

 guishes a flame. Test one jar of 

 the gas by means of a lighted 

 match or taper. <>lerve that the 

 gas burns at the mouth of the jar 

 and that the taper is extinguished 

 when thrust into the tube ; on 



being taken out, the taper again becomes alight on passing through the 



flame of the burning hydrogen (Fig. 102). 



FIG. 102. The hydrogen burns at the 

 mouth of the jnr, but the candle is extin- 

 guished when inside the jar of hydrogen. 



FIG. 103. Hydrogen is lighter than 

 air and can be poured upwards. 



FIG. 104. Hydrogen being licliter 

 than air can be collected by upward 

 displacement. 



