Properties of Liquid Mixtures 



45 



the apparatus is shown in the accompanying 

 it consists of a boiling-tube A about 15 cm. 



sketch (fig. 1); 

 X 3, closed at the 



top by a cork with two holes. Through one passed the ther- 

 mometer — a short one with milk glass scale 40° to 60° in 1 ; 



its bulb was surrounded with a little 



cotton-wool, and an end of the wool 



hung clown into the liquid, so that the 



bulb was always moist ; if that is the 



case, and the stem does not touch the side 



of the boiling-tube, the readings are very 



trustworthy. Through the cork there 



passed also a tube B, about 9 mm. wide, 



surrounded by a short condenser, bent 



at right angles above, and leading to (1) 



a mercury manometer, (2) a T-piece, of 



which the vertical limb passed into a 



Winchester, serving as a reservoir of air, 



and containing a little strong sulphuric 



acid ; and the further limb a glass tap. 



The necks of the boiling-tube and of the 



Winchester were surrounded by a short 



piece of wide rubber tubing each, and 



the corks drowned in mercury ; the only 



other joints in the apparatus were the two 



rubber tubing joints of the manometer 



and the glass tap ; it could be made ab- 

 solutely air-tight without trouble. On 



the far side of the glass tap was placed a 



T-piece leading to a hand air-pump on 

 one side, and on the other into the atmo- 

 sphere, through a long capillary glass tube which served to 

 reduce the flow of air ; the pressure in the apparatus could 

 thus be adjusted with any degree of nicety. The boiling-tube 

 contained about 10 to 15 grams of liquid mixture, previously 

 made up by weighing, and a piece of pumice-stone weighted 

 with copper wire, to make the ebullition steady ; although the 

 thermometer was surrounded by vapour, its readings were 

 never constant unless the liquid was boiling freely. Heat 

 was applied by means of a water-bath, consisting of a two- 

 litre beaker, heated over a sand-tray, with a small flame ; 

 this was provided with a stirrer and thermometer, and kept 

 three or four degrees above the temperature at which the 

 mixture boiled. 



An experiment consisted in weighing out a mixture, taking- 

 its refractive index by the Pulfrich refractometer 5 placing in 

 the boiling- tube, and after adjusting temperature and pres- 



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