Kreder— Quantitatwe Determination of Perchlorates. 293 
The method is essentially the collection of the oxygen of the 
perchlorate; its subsequent passage into an atmosphere of 
nitric oxide over a strong solution of hydriodic acid, and the 
titration of the iodine thus liberated with decinormal arsenic 
in alkaline solution. The apparatus employed consisted of a 
piece of combustion tubing 10 or 12cm. in length, drawn out at 
one end to a narrow restriction of length sufficient to prevent 
the action of the heat on the rubber tubing connecting it with 
a receiver filled with caustic potash. The tube must of course 
be cleansed from all organic materials and cannot be safely 
employed for more than three fusions. A platinum boat 
(porcelain fusing to the glass) served for the introduction of 
the perchlorate to the combustion tube, and in order to bring 
about a gradual and quiet fusion the perchlorate was covered 
with a small amount of an equal mixture of dry and pure sodium 
and potassium carbonates. Carbon dioxide obtained from a 
Kipp generator, the acid and marble of which had been pre- 
viously boiled to expel all traces of air, and to which a little 
cuprous chloride had been added to take up any oxygen which 
might be absorbed from the top, was passed through a solution 
of iodine in potassium iodide to remove a trace of reducing agent 
which it was found to contain, and then washed with potassium 
iodide solution before being used. The larger end of the combus- 
tion tube was closed with a perforated rubber stopper by which it 
was attached to the carbon dioxide apparatus. After all air had 
been expelled from the inclined tube by means of carbon 
dioxide, it was connected by a short glass capillary and vacuum 
tubing joints with the receiver, into which about 50 to 100 cm* 
of gas was allowed to flow before the combustion was started 
and thus when onlyasmali but inevitable bubble remained 
insoluble in the caustic potash the complete removal of air was 
indicated. To prevent the caustic potash from drawing into 
the combustion tube, a little more carbon dioxide was entered, 
when the current was closed by a pinch cock on the side 
towards the generator and heat gradually applied—with perfo- 
rated asbestos cards on either side to check its radiation to the 
rubber—and continued till the contents of the platinum boat 
was in a quiet state of fusion. By lowering one of the bulbs 
of the caustic potash receiver, the oxygen was evolved under 
slightly diminished pressure and thus the chances of loss 
decreased. Then the tube was again inclined and carefully 
annealed while a current of carbon dioxide carried all of the 
oxygen into the receiver, which was then closed and discon- 
nected. As a receiver, two leveling bottles were found vastly 
superior to a burette; the glass stop-cocks of the latter giving 
continual trouble by the action of the caustic potash upon them. 
I found that gas could be removed from a leveling bottle with- 
Am. Jour. Sc1.—Tsirp Series, Vou. L, No. 298.—OctToBer, 1895. 
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