136 Scientific Proceedings, Royal Dublin Society. 



from the variation of distillation constant with dilution that this factor 

 should not be neglected. Similarly, the presence of non-volatile impuiities 

 in the solution may have a considerable influence on the result. 



A comparison of butter-fat with other edible fats and oils shows that 

 while most of the fats are glycerides of acids of higher molecular weight 

 than caproic, butter contains an appreciable amount of butyric acid. It 

 might be expected that the acids from butter-fat could be distinguished 

 from those of the other fats by their distillation constani. Preliminary 

 experiments confirmed this view, and a method has been worked out for 

 determining the distillation constants of the volatile acids in fats. 



Tlie principles underlying the distillation of dilute solutions have been 

 applied in certain industrial processes. In the purification of alcohols, use is 

 made of the fact that in dilute solutions the higher alcohols are removed more 

 rapidly than the lower ones. This is the principle involved in the Guillaume 

 stills for alcohol distillation. A dilute solution of the raw spirit is distilled 

 when the fusel-oils are removed in the first portion of the distillate, while an 

 aqueous solution of ethyl alcohol remains in the still. 



The addition of salts, in increasing the distillation constant of acetic acid, 

 is the basis of one of the methods which have been employed for obtaining 

 concentrated acetic acid from dilute aqueous solutions. It is uneconomical 

 to do this by simple fractionation of the vinegar. The method as used 

 industrially consists in distilling the dilute solution in presence of a salt, so 

 that the distillate is richer in acetic acid than the original solution. 



The Bistillation of Aqueous Solutions of Laurie and Myristic Acids. 



In order to determine if the increase in the distillation constant was 

 general as the homologous series ascended, the constants of lauric and 

 myristic acids have been determined. 



These acids occupy in the fatty acid series a position removed from acetic 

 and butyric acids. They are almost completely insoluble in water ; con- 

 sequently it may be assumed that heat of solution and volume changes 

 on mixing are eliminated. 



A known weight of the pure acid was added to a known volume of 

 distilled water. The resulting mixture was then distilled in a round- 

 bottomed flask, surrounded by a steam-jacket, in the same way as described 

 for previous experiments. It was found that on conducting preliminary 

 experiments, a considerable amount of the acid solidified in the condenser, 

 and vitiated the results to some extent. 



The defect was remedied by using a special condenser arranged so that it 

 could be kept at a temperature above the luelting-point of the acid used. 



