THE PHYSICAL PROPERTIES OF METHYL-ALCOHOL. 



517 



mercury columns were left ?mcorrected for temperature, as we aimed only at 

 comparisons. The following table gives the results of one of a number of series 

 of observations ; v stands for the volume of vapour in the right limb (where the 

 air had not been removed) ; the vapour volume in the left was not much 

 different from v in any case : — 



V 



in c.c. 



Vapour Tension. 



Unboiled, 

 mm. 



Boiled, 

 mm. 



11-5 

 9-8 

 8-1 

 6-3 

 4-7 

 31 

 1-1 

 Max. — Mia. 



412-6 

 412-8 

 413-0 

 4130 

 412-8 

 413-3 

 416-2 

 3-6 



409-7 1 

 409-5 J 



4io-i r 409 ' 9 =*= °' 3 



409-8 

 4102 J 

 411-8 

 2-3 



Other similar series of determinations with the identical samples gave 

 substantially the same results. There would be no use in troubling the reader 

 with any further account of our tensiometric and specific gravity tests ; we 

 prefer to give our general conclusion, which was that our methyl-alcohol, 

 although of a high order of purity, was not sufficiently pure to do justice to even 

 our (home-made) apparatus for measuring the tension of a given vapour. But 

 what could we do towards the further purification of our substance ? The 

 only course we could think of was to determine the tension-curve of the alcohol 

 as it stood up to about its boiling-point ; to then subject it to some kind of 

 chemical purification (say conversion into formate, purification of the same, 

 and regeneration of the alcohol from the purified ester), to determine the 

 tension- curve of the purified alcohol, and compare it with that of the original 

 preparation. Our tensiometer would have enabled us to determine correspond- 

 ing differences of tension with a very high degree of certainty. 



Supposing these differences to exceed the limits of observational errors, 

 the second alcohol must be purified again, say by the oxalate method; and so 

 on until two successive tension curves coincide practically. The mean curve 

 could confidently be adopted as the tension-curve, and the last alcohol as 

 sufficiently pure for any physical determination. 



This, indeed, had been our programme from the first ; but at the end of our 



I pioneering experiments our available time had very nearly been exhausted. 



We accordingly decided upon just accepting our alcohol as the best apology for 



the ideal substance which we were able, under the circumstances, to produce, 



and using it for what we were forced to let stand as our final determinations. 



VOL. XXXIII. PART II. 



4g 



