Kreider— Quantitative Determination of Perchlorates. 295 
was closed and the bulb disconnected and lowered into a solu- 
tion of hydriodic acid of approximately known strength, 
obtained by acidifying potassium iodide with hydrochloric acid. 
When the desired amount of liquid had been drawn in, the 
stop-cock was closed and connection made with the carbon 
dioxide, by which all residual air was expelled. Then the bulb, 
held so as to prevent the escape of the liquid, was again exhausted 
by attachment to the pump. After about 10cm* of nitric 
oxide were admitted, attachment was made to the receiver con- 
taining the oxygen, which was allowed to enter slowly under 
the diminished pressure within the bulb, and with continous 
shaking of the contents of the latter. The latter precaution is 
essential to the process, as otherwise there is imperfect distri- 
bution of the hydriodic acid and the danger of forming nitric 
acid. But when the solution of hydriodie acid is kept strong 
and the shaking continued while the oxygen enters and fora 
minute or two afterward, depending on the rapidity with which 
it was admitted, the oxygen may be allowed to enter quite 
rapidly without any fear of imperfect action. The oxygen 
being immediately utilized, the partial vacuum is effected only 
by the heat generated, which is scarcely noticeable. Asa rule 
the bulb and contents were well cooled before the oxygen was 
admitted. 
It is necessary of course to prevent the access of air into the 
bulb until the acid has been neutralized, to accomplish which, 
without loss of iodine, potassium carbonate must be used, at 
least for the end reaction. Toremove the contents of the bulb 
for titration, the two delivery tubes were filled with water, 
after removing all sodium hydrate from the one through which 
the oxygen was entered; the shorter end connected to a sup- 
ported funnel containing a saturated solution of bi-carbonate 
_and the longer one inserted into an Erlenmeyer beaker contain- 
ing a saturated solution of bicarbonate in amount sufficient— 
as previously determined—to neutralize all the acid taken. By 
opening that stop-cock the delivery tube of which reaches 
below the liquid in the beaker, the bi-carbonate is drawn in by 
the partial vacuum, with liberation of sufficient carbon dioxide 
to force all the liquid out. Owing to the consequent efferves- 
cence as the liquid gains its exit, the flow must be regulated by 
the stop-cock so as to avoid loss of iodine, which is prevented 
by inclining the beaker so that the bubbles strike against its 
side instead of being allowed to splatter out of the opening. 
To wash out the bulb, it is raised almost horizontally, so as to 
prevent the liquid from running through, and the upper stop- 
cock opened to admit the bicarbonate from the funnel. Both 
stop-cocks are then closed, the bulb disconnected and agitated, 
after which it may be washed with water and admission of air 
