Eobeetson. — Molecular Complexity of Fatty Acids. 453 



on the mean. Van't Hoffs law, of course, only applies to 

 infinitely dilute solutions, but even then the results appear to 

 be little or no more in agreement. Thus, for a fall of 0-2° 

 stearic and lauric acids give by a slight interpolation the num- 

 bers 81 and 66, and these acids are both normal fatty acids. 



Calculating the results from Van't Hoff's equation, 

 D = -02T 2 /w, where T is the melting-point on the absolute 

 scale and w the latent heat of fusion, we arrive at the result 

 69. Using, on the other baud, the expression proposed by 



myself,^ D = -0087 MT/Vl (for mono-derivates of benzene), 



the value of D becomes 54, which is abnormally low.f The 

 possibility here presents itself, however, that this irregularity 

 may have some connection with the varying values obtained 

 for the molecular depression. 



About 1897 a large number of interesting cryoscopical 

 researches were carried on by the Italian school of chemists. 

 Paterno examined, among other solvents, the behaviour of 

 phenol for many compounds, his aim apparently being to 

 examine substances of all types and not to confine himself 

 to any one particular group. From his observations he con- 

 cludes that phenol is different from most solvents in that 

 there is a tendency for the molecular weights to decrease 

 with the concentration, whilst in general the reverse is found 

 to be the case. 



The apparatus used in these experiments is essentially 

 that described by Easterfield and Bee, I only the stirrer is of 

 glass and a side tube is added in order to introduce the sub- 

 stance under investigation more conveniently. Of course, a 

 more accurate thermometer is employed : the instruments 

 used in the investigation could be accurately read to a 

 hundredth of a degree. 



The mode of experimenting is as follows : 10 to 20 grams 

 of phenol are weighed into the apparatus and two readings of 

 its freezing-point taken. Enough of the foreign substance is 

 now introduced either from a small weighing-tube if a solid 

 or from a Sprengel pipette in the case of it being a liquid to 

 cause a depression of about three-quarters of a degree. After 



* Trans. N.Z. Inst., 1901, 501. 



t Other phenolic compounds give concordant results with those 

 obtained by actual experiment. Thus for the following substances the 

 calculated values are given, the equation being for multi-substituted 



benzenes, D = -0078 MT/v"E 



Parabromphenol . . . . 99 (experimental 98) 



Orthonitrophenol . . . . 74 ( „ 74) 



Thymol . . . . . . 70 ( , 74) 



J Trans. N.Z. Inst., 1901, 497. 



