Organic 2 Review Problem 458

Organic 2 Review Problem 458 - 442 P RACTICAL O RGANIC C...

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442 PRACTICAL ORGANIC CHEMISTRY Then as before if : g g. of solute in G g. of solvent elevate B.P, by T 0 C., ——-^ =, — g. of solute in ioo g. of solvent elevate B.P. by K 0 C. Cj X 1 «= Molecular Weight of the solute. NOTE, (i) The success of this method depends primarily on obtaining smooth steady boiling of the liquid in T with an absolute minimum of superheating. It is advisable before starting the determination to roughen the end ot the plati- num wire inside T by means of a piece of emery paper wrapped around the end of a glass rod. If, in spite of the presence of this wire and the glass beads, steady boiling is not obtained, better results can sometimes be obtained by preparing a fine roll (2-3 mm. diameter) of thin platinum foil F (Fig. 81), and then cutting it completely across (as shown on the dotted lines) to make a number of triangular cross-sections: add about ten of these to the glass beads. (2) It should be borne in mind that any variation of the rate of heating will
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