100 
PROFESSOR W. RAMSAY AND DR. S. YOUNG 
The Hofmann’s tube was exhausted, filled with mercury, and jacketed with bromo- 
naphthalene, boiling at 752*3 millims. pressure; the temperature was, therefore, 280°, 
at which the vapour-pressure of mercury is 157*35 * millims. 
I. Height of barometer as read on scale 
,, mercury in Hofmann’s tube . . 
115*0 millims. 
. . . 272*3 „ 
Difference. 
Correction for heated column of mercury 
. . . 157*3 
. . . 13*3 „ 
Pressure. . . . 
Pressure reduced to 0 U . 
Weight of ammonium chloride. 
. . . 170*6 
. . . 169*7 
0*00434 grm. 
The ammonium chloride was introduced while 
following readings were taken :— 
the tube was still hot, and the 
Height of barometer as read on scale 
,, mercury in Hofmann’s tube. 
112*8 millims. 
.... 359*1 
Difference. 
Correction for heated column of mercury . 
.... 246*3 
.... 9*3 „ 
Pressure. 
Pressure reduced to 0°. 
255*6 ,, 
.... 254*6 
The tube containing ammonium chloride carried with it a little air, the pressure of 
which, at the higher temperature and volume, was calculated to be 0'25 millim. 
Volume before addition of ammonium chloride.43’9 4 cub. centims. 
,, after ,, ,, „ .63'50 ,, 
Pressure due to air at smaller volume.1697--157'35 millims. 
n 12-35 x43-94 0> „ 
„ „ larger „ .... -—-= 86 
bo o 
Total pressure due to air at larger volume . . 8*6-|-0*25 = 8*85 ., 
Pressure due to NH 4 C1 .... = 254*6 —157*35— 8*85 = 88*4 ,, 
Vapour density of NH 4 C1(H = 1). 13*29 ,, 
Vapour density of NH 3 +PI Cl. 13*37 ,, 
The body is thus seen to be totally dissociated. 
II. Weight of substance. 0*0087 grm. 
Barometer, corrected. 749*4 millims. 
Temperature of bromonaphtlialene vapour . . . 279*8° 
Vapour-pressure of mercury.156*6 millims. 
* In revising proofs, we have substituted for the vapour-pressures of mercury determined by ReGNAULT, 
our revised numbers, which we believe to be more accurate.—[May 22, 1886.] 
