528 



Scientific Proceedings, Royal Dublin Society. 



Fig. 3 shows the relation between the volume of solution distilled and 



the value log for the single acids. 



In Table 9 is given the distillation constant 44tt — for normal acids 

 ° 100 - p„ 



from formic to caprylic and also for isobutyric, isovaleric and isocaproic 



acids. For isovaleric, heptoic, and caprylic acids Dyer's data have been 



employed to calculate the constants. 



Table 9. 



From Table 9 it will be noticed that for each addition of a CH, group to 

 the series of normal fatty acids there is an approximately regular increase in 

 the distillation constant, while if these constants are plotted against the 

 number of CH 2 groups present, the curve obtained (fig. 4) approximates to a 

 straight line. There is evidently a definite relation existing between the 

 rate of steam distillation and the chemical constitution of the fatty acids. 

 Experimental results have been obtained which indicate that the above con- 

 nexion between the rate of steam distillation and the chemical constitution 

 holds in other types of organic compounds, such as phenols, amines, etc., and 

 this line of investigation is being followed up. The distillation constants are 



proportional to -^. Since the density of the water vapour in the flask is 



practically constant, the distillation constants become proportional to -p, that 



is, proportional to the value for the distribution of acid in the aqueous and 



