Lesson IX.] 



CHEMISTRY. 



121 



flask may burst. 5. When gases are to be kept for any length of time grease the 

 stoppers of the receirers. 6th. Do not collect gases too long before they are required 

 for use, as they are apt to deteriorate. 7th. As some gases are soluble in water be 

 careful in their preparation. 



QUESTIONS. 



10 K r._What is oxygen ? 



1'. One of the most widely dif- 

 fused elementary bodies, and therefore 

 placed first among the gaseous bodies. 



105. T. What i< the name derived 

 from, and by whom was it discovered ? 



/'. It is derived from two Greek words, 



oxttte (dvs), acid, and gennao (ytvvaw), 



I give rise to ; and therefore means the 



acid-maker. It was discovered in the year 



"L-heele in Sweden, and Dr. 



Priestley, in England ; the former called it 



al air, and the latter vital air ; but 



er named it oxygen. Its specific 



is 1.1057. 



106. T. How is oxygen obtained ? 



/' By mixing one-fifth of black oxide 



of manganese with four-fifths of dried 



chlorate of potash, and placing them in a 



flask, as in Fig. 29, then applying heat, 



and placing the end of the gas-delivering 



tube under the receiver. By this means 



the whole of the oxygen is given off from 



the chlorate of potash, with greater facility 



n oxide of manganese is not used. 



T. Is this the only method of 



1 the gas ? 



/'- iy be obtained by using 



* short tube of hard glass, fitted with a 



-d cork and bent tube, and sup. 



ans of Gay Lussac's Holder, 

 "), and em|>. 



(red prcn, ,d of chlorite 



Of potash ; but a better way is to use the 



same apparatus as before (Fig. 29), and 

 place chlorate of potash in the flask by 

 itself, and as soon as it boils the gas will 

 be given off'. 



108. T. Describe some of the proper- 

 ties of the gas. 



P. In order to do this I must make 

 some experiments. I have a jar of the 

 gas, and as I wish to plunge some sub- 

 stance into the jar, I must turn it up. 

 Observe, I grease this square piece of 

 glass well on one side, and place the 

 greased side under water against the 

 mouth of the jar, and now I can turn it 

 up and place it on the table without any 

 fear of the gas escaping [Experiment 14]. 

 ,i piece of copper wire, and you 

 see that the end is turned up, thus. 

 Now I will fix a small piece of wax 

 candle to the part that is turned up, 

 I. and pass the wire through a cork that 

 w fits the bottle exactly [Does so]. If 

 ng. 3i we light the candle and blow it out so 

 as to leave a red-hot wick, and then plunge 

 it into the jar, it will ignite and burn with 

 a brilliant flame [Performs the Experi- 

 ment]. Although oxygen burns so bril- 

 liantly now, yet it will not burn by 

 and is therefore called a non-combustible, 

 but a supporter of combustion. 



109. T. Give me some other illustra- 

 tions of its properties. 



P. [Experiment 1.3. J Here is another 

 j r of the gas, and you see that instead 

 of the candle, I have a piece of red-hot 

 charcoal attached to the wire, and, * 

 plunge it into the gas it will bur: 

 [.Performs the Exper- 

 Now, although this is very lu-.-uitiful, it 

 falls far short of another I will show you. 



.:m-nt Ki.J Hrre is a ; 

 iron wire coiled round to look like a cork- 

 has been heated T< 



by holding it over the spirit-lamp, 

 plunge it into the jar of gas. 



:-(.] You i.irhaa 



. thin was because I did not take 

 the precaution to ue a jar < \ 

 ends, and the red-hut metal, winch you saw 



