1G0 Royal Society : — Messrs. Dupre and Page on the Physical 



the composition of the mixture was retained as uniform as possible. 

 Thus estimated, the barometer standing at 744*4 millims., the boil- 

 ing-points are given in the preceding Table. 



Section 4. Capillary Attraction. 



This was estimated by carefully observing the heights to which 

 the several mixtures rose in a capillary tube 0*584 millim. in diameter. 



These heights were measured by means of a telescope and a mil- 

 limetre-scale etched on a glass rod. This glass rod was fixed to the 

 capillary tube, and terminated at its lower extremity in a point, 

 which was made just to touch the surface of the liquid. 



Several precautions were necessary to render the measurements ac- 

 curate. 



The results are contained in the following Table : — 



Percentage 

 of alcohol, by 



weight. 



Height, assuming 

 water 



Relative molecular 

 attraction. 



Height calculated. 



Difference. 



= 100 millims. 









o 



IOO'OO 



ioo-oo 



IOO'OO 





IO 



69-17 



68-07 



93'n 



-25-04 



20 



56-43 



54^3 



86-22 



-3 1 '39 



3° 



48-19 



4 6-I 5 



79-34 



-33-19 



40 



45-3° 



42-56 



7245 



-29-89 



45 



4374 



40-64 



69-00 



-28-36 



5° 



42-93 



39'43 



65-56 



-26-13 



60 



42-30 



37-89 



58-68 



-20-79 



70 



41-76 



36-42 



5*79 



-i5'37 



80 



41-29 



35'°3 



44-90 



- 9-87 



90 



4°"54 



33-35 



38*02 



- 4-67 



100 



39-21 



3i-i3 



3i-i3 





The third column gives the length of a column of water equal in 

 weight to the thread of alcoholic mixture contained in the second 

 column, and gives, therefore, a measure of the relative strength of 

 the molecular attraction in the various mixtures. 



The experiments were made at a temperature of 16° C. 



Section 5. Rate of Expansion. 



This was determined by estimating the specific gravity of the dif- 

 ferent mixtures at the temperatures 10° C, 15°*5 C, 20° C. 



The specific-gravity bottle has two necks ; into one was fitted a ther- 

 mometer with a long bulb, whilst the other ended in a capillary tube. 



This bottle was placed in a water-bath, whose temperature was 

 under perfect control, and thus the specific gravity could be accu- 

 rately estimated at the above-named temperatures. 



Section G. Compressibility . 



This property was estimated by an apparatus similar to the one em- 

 ployed by Regnault and Grassi, but of simpler construction. 



The piezometer was of glass; pressure was applied to the inside 

 and outside by forcing air into the apparatus by means of a small 

 pump ; 0*000002 was always added as a correction for the compres- 

 sibility of the piezometer. 



The two following Tables give the results obtained in Sections 5 

 and G. 



