88 APPENDIX. 



4. Oxygen gas is most easily prepared by mixing to- 

 gether equal weights of chlorate of potash and black 

 oxide of manganese, putting the mixture into a common 

 Florence flask, and applying a spirit-lamp (see Fig. 6). 

 "With a piece of India-rubber tube, or thin lead pipe, 

 the gas may be collected in bottles, as seen in Fig. 8. 

 When filled, they may be corked tightly. Into a bottle 

 of oxygen put a lighted taper (Fig. 4) ; show the bril- 

 liancy of the flame. In the same manner introduce a 

 small piece of ignited charcoal ; and next, a piece of 

 very thin iron wire, to the lower end of .which a little 

 bit of brimstone is secured, and ignited. Show how the 

 iron is consumed. 



Before igniting the wire weigh it, and again weigh 

 the mass after burning, and it wil] be found to have 

 increased in weight, by combining with some of the oxy- 

 gen, forming oxide of iron. Fig. 5 shows a method 

 of exhibiting some of the effects of oxygen, without any 

 of the ordinary apparatus. Into an open tube a small 

 quantity of the mixture of chlorate of potash and oxide 

 of copper may be placed, and the heat of a lamp 

 applied. 



5. Nitrogen maybe prepared by mixing sal-ammoniac 

 with half its weight of saltpetre, both in fine powder 

 and perfectly dry, and heating them in a retort over a 

 lamp. The gas maybe collected as in Fig. 8. Put into 

 a bottle of nitrogen a lighted taper ; its flame is instantly 

 extinguished, and the gas is not ignited, as was the hy- 

 drogen. Nitrogen is also formed by burning phosphorus 

 in a bottle of common air; the oxygen combines with 



