256 
MR. J. J. MANLEY ON THE APPARENT 
to a conclusion by opening the tip of the manometer under mercury; when this was 
done, a considerable quantity of gas escaped from the reaction flask; the bulk of this 
was caught in a tube previously filled with mercury. An analysis showed that the gas 
consisted of nitrogen and nitric oxide, their volumes being approximately in the ratio 
of 1 : 2. 
The determination of the cubic coefficient of expansion of the flask for pressure was 
next undertaken, in order that we might be in a position to calculate the changes in 
the apparent weight of the flask resulting from the related variations in the buoyancy 
of the air. 
The pressure coefficient of expansion was measured with the aid of the apparatus 
represented in fig. 5. The flask, previously emptied and dried, was introduced into a 
small bell-jar and its neck passed up through a cork securely fixed in the mouth of 
the jar ; the wide open end of the jar was then closed by means of a stout iron plate, 
p, which was attached with cement. The jar, together with 
tlie tube t, were next completely filled with air-free water, and, 
except when in use, the fine capillary jet in which the tube t 
terminates was kept immersed in water. In measuring the 
pressure coefficient, the water was removed from under the 
jet and a small weighed capsule substituted for it; air was 
then forced into the reaction vessel until the internal pressure 
was equal to 3 atmospheres, as indicated by the sealed 
mercury manometer m ; as the pressure distended the flask, 
water was ejected through t into the capsule, which was then 
removed and again weighed. With slight modifications the 
contraction coefficient of the vessel was also determined. 
Both determinations were carried out several times and the 
pj„. 5 _ results obtained were very concordant. It was thus found 
that an additional pressure of 1 atmosphere increased the 
volume of the reaction vessel by an amount equal to '02 c.c. The weight of ‘02 c.c. 
of air may be taken = ’024 mgr., and this is therefore the change produced in the 
buoyancy effects of the air upon the flask by a pressure = 760 mm. of mercury. We 
now give in Table VIII. which follows a summary of the results obtained during this 
branch of our inquiry. 
The contents of Table VIII. are almost sufficiently self explanatory. It may be 
seen that on mixing the two reacting bodies, two hitherto absent variables the one 
dependent upon the other, were unknowingly introduced; there were prolonged, 
unsuspected and complicated chemical changes producing an irregular temperature 
and cOiaSequent loss in the buoyant properties of the air enveloping the reaction vessel; 
and as a necessary result of the chemical changes, a quantity of gas with its attendant 
pressure was generated within the vessel which, becoming distended, displaced 
additional air and was thus rendered more buoyant. The observed fiuctuatioiis in the 
