Soft water, definition

Application of ion exchange refining to the process for the manufacture of dextrose may be understood from the following description of such a process. Triple-washed starch is diluted with ion-free water to the desired concentration and is acidified with a definite quantity of mineral acid such as hydrochloric or sulfuric. It is desirable that the acidified starch slurry be held for at least thirty minutes in order to permit an effective equilibrium acidity to be reached. The starch slurry may contain a quantity of soft water salts which consume acid, and since this consumption is variable, the acidity is checked and adjusted to the desired level following the holding period. The conversion is then carried out at elevated temperature and under pressure for a period sufficient to yield maximum dextrose. The conversion may be carried out batchwise in an autoclave, or continuously. 

Cross-linked versions of water-soluble polymers swollen in aqueous media are broadly referred to as hydrogels (52) and have a growing commercial utility in such apphcations as oxygen-permeable soft contact lenses (qv) (53) (Table 4) and controUed-release pharmaceutical dmg deflvery devices (54). Cross-linked PVP and selected copolymers fit this definition and are of interest because of the following stmcture/performance characteristics ... 

It is worthwhile to point out some obvious anomalies in HSAB theory. Some ligands do not show definite hard or soft behaviour. Consider OH- which reacts with most central atoms in M(II) and M(III) with the exceptions of Ca, Sr, Ba, Eu and Ra irrespective of the softness of the central atom. This behaviour is probably due to the consecutive deprotonation of ligated water molecules to hydroxy and then to oxo complexes which is pH dependent and due to increase in ionic potential Z/rl0n. 

Since water is a hard solvent, the Gibbs energy of transfer of ions from water as a reference solvent to other solvents should depend on the softness of these solvents in a different manner for hard and soft ions. For ions of equal charge and size, hard ions should prefer water and soft ions the softer solvents. The definition of p by Eq. (7-12e) has been given because the size of the soft Ag ion is intermediate between those of hard Na and K . The p values for 34 organic solvents have been determined e.g. p = —0.12 for 2,2,2-trifluoroethanol, 0.00 for water (by definition), 0.64 for pyridine,... 

Definition Obtained by solv. extraction of the dried rhizomes of Curcuma longa Properties Bright yel. powd. or yel. orange to red brn. vise, liq. soft spicy woody earth odor mustard taste misc. with water Toxicology Human mutagenic data Hazardous Decomp. Prods. Heated to decomp., emits acrid smoke and irritating fumes Uses Natural flavor in foods and pharmaceuticals... 

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