Hardness hydrogen

As a general rule flasks and similar vessels should be heated in an air bath (compare Fig. II, 5, 3). A glycerol bath may be employed for temperatures up to 140° the glycerol is subsequently removed from the outside of the vessel by washing with water. Medicinal liquid paraffin may be used for temperatures up to about 220° hard hydrogenated cotton seed oil, Silicone fluids or fusible metal may be employed when higher temperatures are required. Small test-tubes and centrifuge tubes... 

Hard hydrogenated cotton-seed oil (m 40-60°) or a 1 1 mixture of cotton-seed oil and castor oil containing about 1% of hydroquinone. 

Now let us turn our attention to hydrogenation reactions. Certain hydrogenation catalysts are highly substrate specific. While a combination of C0CI2 and AIR3 (hard) hydrogenates both ot-olefins and dienes, in the presence of phosphine or phosphite, the diene is preferentially hydrogenated in the mixture (soft-soft interaction). 

Guanidinium ion acts as a guest in the ethereal cavity during cyclization of compound 3. A template effect is achieved through specific hard-hard hydrogen bondings (5). 

NB - The provisions for hardness, hydrogen ion concentration, dissolved oxygen and calcium also apply to desalinated water. 

Moreover, all cation-anion interactions are mismatching according to the HSAB-concept that is, soft sulfur only interacts weakly with the hard hydrogen in the cation [50]. The combination of both effects appears to lead to low melting and low viscosity tetrathiocyanatocobaltate(II) ionic liquids. 

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