STUDY OF THE ACTIVE PART OF THE AIR 129 



ii. The burning of a candle in oxygen. Attach a piece of stout wire 

 to a wax taper and having lighted the taper plunge it into another of the 

 jars of oxygen. Notice that it is not extinguished, but continues to burn 

 and with a larger and brighter flame. 



iii. The burning of charcoal in oxygen. Into another jar of oxygen 

 thrust a splint of wood red-hot at the end, or a piece of red-hot charcoal 

 placed in a deflagrating spoon (a small up- 

 turned iron spoon with a long handle) (Fig. 96). 

 Note the brilliancy of the combustion. Now 

 pour into the jar some clear lime-water (i.e. 

 some of the clear liquid which is formed if 

 lime and water be shaken together and allowed 

 to stand. It is really a solution of lime in 

 water). Notice that it turns milky owing to 

 a white powder being diffused through the 

 liquid. 



iv. The burning of phosphorus in oxygen. 

 In another jar burn a piece of phosphorus 

 about half the size of a pea, contained in the 

 deflagrating spoon. Note the great brilliancy 

 of the combustion and the dense white fumes. 

 Add water and shake the fumes dissolve. 

 Into the solution put a blue litmus paper. 

 Observe that it is turned red. 



v. The burning of sulphur in oxygen. 

 Perform, with another jar, a similar experi- 

 ment with sulphur. There are few fumes, but 

 a strongly smelling gas is obtained, also soluble 



in water, turning blue litmus red. 



FIG. 96.- Jar with deflagrating 



vi. The burning of magnesium ribbon in spoon in it. 



oxygen. Ignite a small piece of magnesium 



ribbon and hold it by means of crucible tongs in a jar of oxygen. Notice 

 the white solid formed. Test its solubility in water, and show that, unlike 

 the previous products, it will not turn blue litmus solution red, but will 

 turn red litmus solution blue. 



vii. The burning of sodium in oxygen. Put a small piece of sodium 

 in a dry deflagrating spoon, light the sodium, put it into another jar of 

 oxygen. Observe the fumes formed. Dissolve these in water and try the 

 effect of the solution on litmus paper. It does not turn the blue colour to 

 red, but has exactly the reverse effect, it changes red litmus to blue. Feel 

 the water ; it has a soapy feel. 



yiii. The burning of iron in oxygen. Obtain some fine iron wire and 

 twist a few strands of it together. Heat in a Bunsen flame, and while 

 white hot plunge into a jar of the gas. Test the solubility of the solid 

 formed. 



Properties of oxygen. Oxygen gas was discovered on August 1st, 

 1774, by Dr. Joseph Priestley, who obtained it by heating mercury 

 calx. In accordance with the theory of combustion prevailing at the 

 time he named it " dephlogisticated air," since substances burned 

 better in it than in ordinary air. 



J.O.S. I 



