ALCOHOLS 65 



3. Absolute Alcohol. 



Rectified spirit is filtered through charcoal and fractionally distilled, 

 the first portions which contain aldehyde and the last portions which 

 contain fusel oil being rejected. The middle fraction is distilled over 

 quicklime and commercial absolute alcohol is obtained. This contains 

 about -5 per cent, of water. Pure alcohol is prepared from this by 

 adding the requisite quantity of metallic sodium or calcium and again 

 distilling. 



4. Absolute Alcohol from Methylated Spirit. 



Methylated spirit (i litre) is boiled upon a water-bath under a 

 reflux or inverted condenser (p. 18) with about 30 gm. of caustic soda 

 for one hour in a 2-litre flask. Acetone, aldehyde and other impurities 

 are destroyed and the spirit turns brown. The contents of the flask 

 are distilled and the distillate collected in another flask of the same 

 capacity containing 400-500 gm. of quicklime. The flask is connected 

 with a reflux condenser and either allowed to stand for twenty- four 

 hours or heated for one hour on a water-bath. The liquid is distilled 

 again without pouring off from the flask. The yield of absolute 

 alcohol is about 80 per cent., 'and it contains 2-3 per cent, of water. 

 By treating it again with half the previous quantity of quicklime the 

 amount of water may be reduced to less than I per cent. The boiling- 

 point (76-78) may be determined by distilling 50 c.c. in a small 

 apparatus. 



Properties. 



(1) Ethyl alcohol is a colourless, pleasant-smelling liquid with a 

 hot taste. It boils at 78 and has a sp. gr. of 79384 at 15-5 

 or 60 F. 



(2) It mixes with water in all proportions. Absolute alcohol is 

 very hygroscopic and readily absorbs water on exposure to the air. 



On mixing alcohol with water there is an evolution of heat and a 

 contraction in bulk. 



The addition of water to methylated spirit produces a cloudiness 

 due to the precipitation of the mineral naphtha. 



(3) Alcohol burns with a faint blue non-luminous flame even when 

 mixed with considerable amounts of water. 



On mixing 10 c.c. of alcohol with 10 c.c. of water in a measuring 

 cylinder the evolution of heat will be noticed, and when the mixture 

 is cold the diminution in volume can be measured. By placing the 

 mixture in a small basin and applying a light it will be seen whether it 

 is or is not inflammable. 



