Page:Outlines of Physical Chemistry - 1899.djvu/81

 SPECIFIC GRAVITY

��certain radicals (OH, CH 3, &c), we generally find that the volatility of the substances is favoured by the two following circumstances :

(a) by the central position in the molecule of the sub- stituting atom or radical.

Examples. —

( (CH^.CH.CHrCH^OH) boiling point 128° to 132° C*H 12 - (CH s ) 2 .CH.CH(OH).CH, „ „ 104° to 108°

��(CH^^CJOHJ.CHj.CH,

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�� ��98° to 102° (Naumann.) r j CHj.CH^CHCls. . boiling point 86<

(Henry), (ft) by the substituting atoms or radicals being close together.

Example. —

ICHjCLCH^CHjCl. . boiling point 119° CH..CHC1.CH2C1. „ „ 96-8°

CH S .CH 2 .CHC1 2. „ „ 86°

CH 8 .CC1 2 .CH S. „ 70°

(Henry).

This regularity applies also to the aromatic series (benzene-derivatives) where the di-substituted ortho- deri- vatives are generally more , volatile than the correspond- c ingpara- derivatives.

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��Specific Gravity

For information concern- ing areometers and pycno- meters the student is referred to text-books on physics. But here SprengeVs pycnometer may be mentioned. The ap- paratus can easily be made from ordinary glass-tubing (fig. 9). The reservoir b ends in two horizontal branches, one of which, c, is a fine capillary tube, whilst the other, b,

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