516 PROFESSOR D1TTMAR AND MR C. A. FAWSITT ON 



The two fractions were mixed, again dehydrated by anhydrous sulphate of 

 copper and distilled, the first few drops of distillate being rejected. Two 

 drops of what followed immediately were shut up in the right limb of the 

 tensiometer ; the distillation was then carried on to near the end, and two 

 drops of the very last runnings collected in the left limb of the tensiometer. 

 A comparison of the tensions gave the following results : — 



t = 30° 50° 65° C. 



Ap = l'3 15 3-0 mm. 



in favour of the earlier runnings. 



The alcohol "D" was now tested, so to say, against itself; the left limb 

 of the tensiometer was charged with only two drops, the right limb with some 

 2 c.c. of the alcohol ; both were boiled before being shut up. A comparison of 

 the tensions at 3 temperatures gave the following results : — 



t =30° 50° 65° C. 



Ap = G-l 7-1 7'9 mm. 



in favour of the larger specimen. 



These results were rather discouraging, because they seemed to show that 

 the alcohol was impure. To show the relevancy of the A;>'s, we add the corre- 

 sponding A^'s, which are 



A£ = 0°-7 0°4 0°'3. 



It however still remains to be proved that the tension of even pure methyl- 

 alcohol is absolutely independent of the ratio of the mass of the vapour to the 

 mass of the liquid which it is in contact with. Methyl-alcohol, in reference to 

 its conversion from liquid into vapour, exhibits anomalies. It "bumps" badly 

 when distilled out of a glass vessel, i.e., it may be heated considerably above 

 its boiling point before it actually boils. According to our experience, it some- 

 times exhibits a similar anomaly in experiments for determining its vapour 

 tension by the statical method. 



The air-free alcohol, when shut up over mercury under a pressure which is 

 considerably less than its maximum tension at the temperature of the bath, 

 may form no vapour at all until the apparatus is being shaken, when a sudden 

 formation of vapour sets in with explosive violence. 



We are here referring to a series of experiments in which the two limbs of 

 the tensiometer were charged with nearly equal quantities of the same alcohol; 

 but only one of the two samples was deprived of its air before being shut up (in 

 the left limb). The temperature of the bath being kept rigorously constant 

 (reading of a sensitive but zmcorrected thermometer 51°7), the tensions of the 

 two samples were determined at a variety of volumes. The heights of the 



