400 Intelligence and Miscellaneous Articles, 
After being cleaned, the apparatus (which now consists of three 
portions, viz, the portion CC hermetically sealed and the two ends 
6 and D) must be weighed, 
‘The capacity of the apparatus is found by filling it completely with 
water and weighing; but previously to this operation the volume of 
hydrogen enclosed at the time of sealing must be found. On break- 
ing one extremity under water, the water will rise in the bulbs, and, 
after a while, will have absorbed all the vapour, but will leave 
the hydrogen, ‘The bulbs must then be lifted out of the water, 
without altering their temperature, and, with the water that has 
entered, weighed. ‘The difference between the latter weighing and 
the weight of the bulbs quite full of water gives the weight in 
grammes, which expresses in cubic centimeters the volume of hy- 
drogen enclosed; the pressure is the height of the barometer minus 
the column of water which had entered the bulbs; the temperature 
is that of the water, 
An example of a determination of the vapour-density of alcohol 
at 30° C. below its boiling point is subjoined ;— 
Height of the barometer (at O° C.) ...... 763°09 millims, 
Temperature of the balance case ......., 75 C, 
Weight of apparatus in dry air,......... 69°959 grms, 
‘Temperature at time of sealing. ......... 48°C, 
Weight of apparatus + hydrogen+vapour,, 69°5275 grms, 
Weight of apparatus+ water (at 3°2C.)., 191°76 grms, 
Weight of apparatus filled with water.... 545°36 grms. 
Height of water column .. ..00. 6 ce eens 122 millims, 
From which is deduced—~ 
Volumes corrected 
at 0 C. and 760 millims. pressure, 
eubie centimeters. Grn, 
Hydrogen+ vapour ...... 40643 weighing 0°1695 
Hydrogen, , .. weap oe Ue 341°27 ”» O0306 
65°16 Or 1389 
Therefore, 65°16 cub. cent. of alcohol-vapour weigh +1389 
but 65°16 cub. cent. of air weigh... ...... ‘0843 
"1389 
Vapour-density of alcohol = = 1648, 
‘OS43 
The authors have extended their experiments to acetic acid and 
other substances. At low temperatures the vapour-density of acetic 
acid approximates to 400, no matter how much hydrogen be em- 
ployed. At higher temperatures an approximation to 2°00 is ob- 
tained, but without heating so high as Cahours found necessary, 
The authorsare continuing these researches. — From the Proceedings 
of the Royal Society of Adindurg’, January 21,1386). 
