14 PRACTICAL AGRICULTURAL CHEMISTRY [32-33 



Choose a dry test-tube and fit a sound cork into the 

 mouth of the tube. Bore the cork, and fit it with a 

 bent tube of the shape shown in fig. 15. Next powder in 

 a mortar about as much potassium chlorate as will fill a 

 small watch-glass, together with about one-fifth as much 

 manganese dioxide. One-third fill the test-tube with the 

 mixture and place it in a retort-stand, as shown in the 

 figure, jtfext place a beehive cell in a larger vessel and add 

 water until it reaches about one inch higher than the top of 

 the beehive cell. Before commencing to heat the tube, fill 

 one of the jars in which the gas is to be collected with 

 water, cover its mouth with a ground-glass plate. Invert it 

 and place it on the beehive cell, as shown in the figure, 

 removing the glass plate when the mouth of 

 the jar is under the water See that the end 

 of the delivery-tube is directly beneath the 

 opening of the jar. Now heat the part of 

 the oxygen mixture (potassium chlorate and 

 manganese dioxide) nearest the cork with a 

 Bunsen flame. Oxygen will come off more 

 readily than in the former case (30), and, 

 passing through the delivery-tube, will be 

 collected in the jar. As soon as one jar is 

 filled with the gas, close it with a glass plate 

 and remove it from 'the earthenware dish, replacing it by 

 another filled with water and inverted in the same manner. 

 When three jars have been filled in this way remove 

 the delivery-tube from the water and discontinue heating. 



32. One of the properties of oxygen has already been 

 shown, i.e. its power of rekindling a glowing splinter of 

 wood. All substances which burn in air burn still more 

 readily in oxygen. 



33. Burning Sulphur in Oxygen.— Place a small 

 piece of sulphur on a deflagrating spoon. Heat it in a 

 Bunsen burner until it ignites, then plunge it into a cylinder 



Fig. 16 



