Abstract
The effects of selected anions on the molecular organization of H2O are elucidated by the 1-propanol (1P) probing methodology developed by us. We determine the third derivative quantity, the 1P-1P enthalpic interaction, HE1P-1P, in ternary system of 1P-sample salt (S)-H2O. In the presence of S, the HE1P-1P pattern changes while keeping the basic peak anomaly. These induced changes are used to elucidate the effect of S on H2O. We found within the sodium salts of SO42-, F-, Cl-, Br-, I- and ClO4- that the first three act basically as hydration centers. The hydration numbers are 17, 14 and 2.3, respectively. The remaining Br-, I- and ClO4- are basically hydrophiles. They form hydrogen bonds directly to the existing hydrogen bond network of H2O and thus work as impurity centers in the existing network, retarding the degree of fluctuation inherent in H2O. Their effects are stronger in the order of Br- < I- < ClO4-. Thus in terms of the Hofmeister effects, the kosmotropes (salting out agents) are hydration centers and the more the hydration number, the stronger the salting out effect. The chaotropes (salting in reagents), Br-, I- and ClO4-, are hydrophiles, and the stronger the hydrophilicity the stronger the salting-in power.
