354 ‘Professors W. B. and R. E. Rogers 
very uniform temperature, so as to dispense with any rubbing of 
the apparatus before weighing, a proceeding which though com- 
monly practiced, frequently leads, according to our observations, 
to much uncertainty in the subsequent counterpoising. This re- 
sult is in part due to the deposition of moisture on the apparatus, 
in the act of weighing, which even in a uniform condition of the 
air as to humidity, must be unequalgin the first and last weigh- 
‘ings, unless the temperature of the vessel, and the time consum- 
ed in the process, be the same in both cases. But a still larger 
share of the effect is chargeable, according to our experiments, to 
the electrical excitement produced in the glass by the friction, 
which, communicated to the scale pan, affects the apparent weight. 
_ We will now briefly sketch our mode of using the apparatus 
in exact research, and describe a further process, which we have 
found necessary for expelling the carbonic acid from the liquid. 
When the bucket is used, a small bit of tissue paper is pressed 
down upon its bottom, so as completely to close the hole, and 
then the weighed carbonate, usually one hundred grains, carefully 
transferred into it. Having charged the bottle with moderately 
dilute hydrochloric or sulphuric acid, in quantity a good deal 
more than is required to neutralize the carbonate, and having 
properly adjusted the cork, we hang the bucket with its contents 
upon the upper hook of the platinum wire, and lifting the appa- 
ratus into the scale by the buckskin holder, we counterpoise it 
with great care. Then withdrawing it from the scale, we lift 
off the bucket, remove the cork, attach the bucket to the lower 
hook, previously drawn up so as nearly to touch the lower side of 
the cork, and again secure the cork in its place. As it now hangs 
the bucket is from one half to three fourths of an inch above the 
level of the liquid. Depressing the wire, we plunge the bucket 
into the fluid, which enters by the aperture below, and varying 
the depth of immersion from time to time, we regulate the efier- 
vescence, so as to be uniformly brisk, but without great violence. 
The effervescence having ended, as shown by the absence of 
any crepitation when the ear is held elose to the flask, the liquid 
is briskly agitated to favor the escape of adhering bubbles, and 
the instrument is now connected with the appendages above de- 
scribed, in the manner indicated in fig. 2. The syphon being 
set in action, and the closeness of the connection ascertained, a8 
before directed, the aspiration is commenced. During this pte 
at 
