104 JUNIOR GRADE SCIENCE 



Gas. Slip a greased plate under the mouth of the gas jar and remove 

 from the pneumatic trough. Note the odour ; add a little lime water and 

 shake thoroughly, and again note odour. Apply a lighted taper. 



Fio. 81. Apparatus for dry distillation. 



Dry distillation of wood. The appearance and many of the pro- 

 perties of wood differ according to the variety under examination. 

 When pieces of wood are heated in a closed vessel and the products 

 solid, liquid, and gaseous are collected separately, it is found that 

 each kind of wood gives much the same products. 



A black solid remains in the test-tube or retort, which is easily recog- 

 nised as charcoal, by its appearance and the way it burns in air when 

 heated. 



The liquid which collects in the cooled receiver contains a little tar 

 and a lighter liquid, which can be shown to be water with something 

 else present, which has a sharp odour and bitter taste and turns litmus 

 red. As a matter of fact it is a mixture of different liquids. One of 

 them acetic acid may be recognised from its resemblance to vinegar. 



The gas is found, after shaking up with lime water, to be colourless 

 and nearly odourless. When a lighted taper is plunged into a jar of 

 the gas it is extinguished, but the gas burns with a blue flame. 



47. EXAMINATION OF SULPHUR. 



i. Examine as described in Chapter XVII. 



ii. Effects of heat upon sulphur. (a) Put some finely powdered sulphur 

 into a large test-tube, using sufficient to fill the tube to a height of about 

 H inches, and heat carefully with a small Bunsen turner flame. Occasionally 

 take the tube out of the flame and shake it. When the sulphur has all 

 melted notice that an amber- coloured liquid has been formed. Pour a 

 little of the liquid into a beaker of water. Observe that a lump of yellow 

 sulphur is again formed, which when broken reveals a crystalline structure. 



(6) Continue to heat the remainder of the liquid sulphur obtained in 

 (a) until the liquid boils. Carefully observe the changes in colour of the 



