366 
DR. MEYER WILDERMAN OX CHEMICAL DYNAMICS 
intensity of light. I omit, however, this correction, because the variations 
in the values of Iv, especially when taken, as in our case, at small intervals, 
are too considerable for the application of very small corrections to be of any 
essential use. 
Sid. gives the sensitiveness of the galvanometer used for the measurement of 
the intensity of light, measured with standard units (manganin resistances 
and Clark), and expressed in millimetre deflection of the galvanometer on 
the same scale. From this the value of (i) is also known in standard units, 
is the actual temperature of the bath on 1° thermometer at the time r. 
t r is the temperature t B read on the 0°T Beckmann thermometer at the same 
time r. 
t man is the temperature of the room near the manometer. 
Since the volume of the gas in the capillary tubes changes during the 
reaction, owing to the rise of the mercury in the same, its value is during 
the reaction from 0‘2 per cent, to 0'5 per cent, of the volume of the gas in 
the quartz vessel or the bulb. 
A variation in the temperature of the room =1° produced a change in the 
height of the manometer from rvnr. ^ A5 percent. ^ ^otal 
pressure of the gas. 
0-2 x 760 
amounts to —- ~—r 
273 x 100 
When the pressure of the gas = 760 millims., this 
= 0'005 millim. to 0'012 millim. per 1° variation in 
the temperature of the room. So long as we investigate only small 
intervals of the curve, i.e., when the temperature of the room could not 
change by 1°, no correction need appear in the tables, and t man _ need not 
enter into the equation. When, however, the curve is investigated at 
greater time intervals, a correction for t man _ can be usefully applied. 
t' r ~t" r is the difference in the temperature of the bath (and gas mixture) at the 
time t' and t", read to 0°'01 on Beckmann’s thermometer. 
t' r -t" r corr. is the correction in millimetre pressure, which is to be added to the 
observed tt'-tt " for the variation of the temperature of the bath. This 
value, when the expansion of the glass bulb is simultaneously accounted 
for, equals l'S millim. for each 1° variation of temperature of the bath. The 
value of the correction was found from direct observations on the manometer, 
by bringing the bulb successively to higher temperatures. This correction 
is especially important when small parts of the curve are investigated, and 
becomes of smaller importance the greater tt'-tt " is, since the variations 
of t remain almost constant during the whole time of the experiment. 
li is the barometric pressure at the time r, read with the vernier ; the temperature 
of the mercury is given in brackets. 
