ON EVAPORATION AND DISSOCIATION. 
2. Agreement of statical ancl dynamical methods of measuring vapour-pres¬ 
sures. (See Regnault, £ Memoires de l’Academie des Sciences,’vol. 26, 
p. 341.) 
3. Comparison of results with those of most careful observers. 
1. Constancy of boiling-'point. (Extracts from Note-book.) 
“Methyl-alcohol prepared from methyl oxalate by action of ammonia: dried 
with barium oxide ; dried with anhydrous copper sulphate ; stood for some weeks 
(see Perkin, £ Chem. Soc. Journ.,’ vol. 45, p. 465). Boiling-point by no means 
constant. 
“Dried with sodium. A good deal boiled constantly at 65'55 c (corr.). Bar. 
= 761‘9 mms. at 0°, and then temperature rose. 
“Dried again with sodium. A good deal boiled constantly at 65°; temp, rose 
slowly to 65‘8°. Bar. same. 
“ Dried again with sodium. Began at 64'9° ; most of it came over within a tenth. 
Temp, rose finally to 65’3°. Bar. same. 
“ Dried again with sodium. Began at 64‘85° ; most of it came over within half-a- 
tenth. Temp, rose to 65’05°. Bar. same. 
“ Dried again with sodium. Began at 64‘8° (or a trace above). Temp, rose only 
to 64'9° (rather below).” 
(All these temperatures are those of Begnault’s air thermometer.) 
Vapour-pressure determinations were then made by our method (‘ Chem. Soc. 
Trans.,’ 1885, January). 
“ Alcohol re-distilled with a little sodium ; B.P. 64‘95°. Bar. = 761’9 mms. (at 0°.)” 
The specific gravity was then taken. 
“Methyl-alcohol re-distilled and fractionated; B.P. 64'7° at 760 mms. (at 0°). 
Range, 0‘05°.” 
Experiments at high temperatures and pressures were then made, and, after these 
were completed, 
“Fractionated alcohol was re-distilled; B.P. 64‘2° at 743 - 2* mms. (corr. to 0°). 
The vapour-pressures were again determined in our apparatus.” 
The accompanying curve on Plate 18 shows the i^°^ n §' P om ^ s 1 of the two 
1 J ® [ vapour-pressures J 
samples of methyl-alcohol. 
2. Agreement of statical and dynamical methods of measuring vapour-pressures. 
a. At low temperatures. No special measurements were made at low temperatures 
by the statical method, but two observations were incidental during the determina¬ 
tion of the volumes of 1 gramme by means of the “ modified Hofmann’s apparatus.” 
These are represented on the curve by large crossed circles. The actual numbers are : 
* Value of dpjdt at 60°, 25'47 ; at 70°, 35'38 mms. Sufficiently correct estimate at 65°, 30 mms. 
Add 0'55°. Corrected B.P. at 760 mms., 64'75°. 
2 u 2 
