Law of Molecular Attraction. 485 



themselves, see Young *. I at that time adopted 2 per cent, 

 as the probable allowable limit of divergence in the constant 

 due to the errors of measurement as compounded and multi- 

 plied in their effect upon the constant, and Dr. Young, who 

 with his co-workers made the measurements, acquiesced. At 

 that time my own results showed many divergences in the 

 constant greater than 2 per cent, from the mean value. I 

 set about finding the reason for these divergences, and as the 

 statement has been made that my equation is probably acci- 

 dental, I would like to call attention to some of the really 

 remarkable " accidents " that have happened in the course of 

 my investigation. 



1. Ethyl oxide. — Unusual variations in the " constant i} at 

 and above 185° caused me to suspect an error in the heats of 

 vaporization as calculated by Ramsay and Young. Young- 

 repeated the calculations at my suggestion and corrected the 

 error f. 



2. Di-isobutyl showed some divergent values of the con- 

 stant which resisted explanation. Finally, in 1906, I wished 

 to measure the substance further, and Dr. Young very kindly 

 agreed to let me have the original substance. On getting 

 the liquid, which had been very carefully preserved in a 

 well-stoppered bottle, small crystals were found in the bottom 

 of the bottle. On pouring off the liquid and attempting to 

 fractionate it, further crystals appeared in the Young's 

 fractionating column and even in the condenser-tubes, the 

 boiling-point of the liquid meanwhile remaining apparently 

 constant. This remarkable fact caused Dr. Young to say 

 that possibly the liquid was impure when measured, a remark 

 he has since taken care to repeat J. I was not able to purify 

 the liquid and could not at the time prepare more, so that 

 no further measurements were made. 



3. Stannic chloride. — The divergences first found, which I 

 originally thought must be due to some decomposition of the 

 substance, were later shown to be due to an error in my own 

 calculations. 



4. Chloro-benzene. — To explain certain divergences at 240° 

 to 270° I suggested in 1904 § that the Biot formula used for 



obtaining the -^ was probably wrong. This explanation 



was shown some five years later to be correct when Young 

 himself recalculated the formula. 



* Sci. Proc. Roy. Dublin Soc. xii. No. 31 (1910). 



t Journ. Phys. Chem. viii. p. 635 (1904). 



+ Sci. Proc. Roy. Dublin Soc. xii. No. 31, p. 384 (1910). 



§ Journ. Phys. Chem. viii. p. 400 (1904). 



Phil Mag. S. 6. Vol. 24. No. 142. OcL 1912. 2 K 



