Organic 2 Review Problem 485

Organic 2 Review Problem 485 - blocked with a glass rod) as...

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QUANTITATIVE ANALYSIS 469 for many determinations the absorbent gradually "cakes," seriously impeding the passage of oxygen, and has to be replaced. This is easily effected by carefully cutting the top off the limb, cleaning it out, refill- ing and sealing once again. By having the projecting length above the side-arm in the first instance this process may be repeated several times without modifying the tube; when the edge finally gets too near to the side-arm a fresh length of tube may be fused on and the whole series repeated. The second limb of the U-tube is similarly filled with magnesium perchlo- rate and sealed off; this packing ensures the final removal of any traces of water vapour from the oxygen stream. It is essential when the limbs are being filled and sealed that the operations are carried out as rapidly as possible and that the side-arms are stoppered (by means of a short length of impregnated tubing
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Unformatted text preview: blocked with a glass rod) as both sub-stances absorb water vapour from the air very readily. The two limbs of the U-tube are separated by a ground-glass tap T 1 . This keeps the two absorbents out of contact with each other except when oxygen is flowing and also shuts the oxygen stream off from the combustion tube. It is an advantage to have all the com-ponents of the purification train mounted on a small rigid framework. Thus pure, dry oxygen is delivered at the combus-tion tube. The combustion tube. The oxygen is led through the side-arm G (Fig. 85) into the combustion tube L via the horizontal side-arm H which is fused into the combustion tube about 4 cm. from the end (the joint between G and H is also made with impregnated rubber tubing with the two glass tubes touching inside the rubber). The posi-tion of H thus allows the combustion...
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