Salted brush

Dry some potassium iodate at 120 °C for 1 hour and allow it to cool in a covered vessel in a desiccator. Weigh out exactly 5.350 g of the finely powdered potassium iodate on a watchglass, and transfer it by means of a clean camel-hair brush directly into a dry 1 L graduated flask. Add about 400-500 mL of water, and gently rotate the flask until the salt is completely dissolved. Make up to the mark with distilled water. Shake well. The solution will keep indefinitely. 

Unpigmented paint samples were brushed onto a potassium bromide crystal or polyethylene sheet (paint film thickness about 5 microns) and stored at controlled relative humidity using saturated salt solutions in closed vessels or a climate controlled room. 

Irrespective of the physical form of the carotenoid in the plant tissue it needs to be dissolved directly into the bulk lipid phase (emulsion) and then into the mixed micelles formed from the emulsion droplets by the action of lipases and bile. Alternatively it can dissolve directly into the mixed micelles. The micelles then diffuse through the unstirred water layer covering the brush border of the enterocytes and dissociate, and the components are then absorbed. Although lipid absorption at this point is essentially complete, bile salts and sterols (cholesterol) may not be fully absorbed and are not wholly recovered more distally, some being lost into the large intestine. It is not known whether carotenoids incorporated into mixed micelles are fully or only partially absorbed. 

The interest in these block copolymer micelles arises from the polyelectrolyte coronal block whose intrinsic properties are strongly influenced by many parameters including pH, salt concentration, and polar interactions. Moreover, they provide a unique model to mimic polyelectrolyte brushes at a high segment concentration, as noted by Forster [15]. 

Salt effects in polyelectrolyte block copolymer micelles are particularly pronounced because the polyelectrolyte chains are closely assembled in the micellar shell [217]. The situation is quite reminiscent of tethered polymer brushes, to which polyelectrolyte block copolymer micelles have been compared, as summarized in the review of Forster [15]. The analogy to polyelectrolyte brushes was investigated by Guenoun in the study of the behavior of a free-standing film drawn from a PtBS-PSSNa-solution [218] and by Hari-haran et al., who studied the absorbed layer thickness of PtBS-PSSNa block copolymers onto latex particles [219,220]. When the salt concentration exceeded a certain limit, a weak decrease in the layer thickness with increasing salt concentration was observed. Similar results have been obtained by Tauer et al. on electrosterically stabilized latex particles [221]. 

At one time, women painted clock and watch dials with luminous radium paint that was a mixture of radium salts and zinc sulfide. They would place the small brushes between their lips and tongue to make the bristles more pointed, in order to paint fine lines with the radium paint. Over the years, they developed cancers that resulted in badly eaten-away and disfigured lips and jaws. Once the danger was known, luminous radium paint was banned for this use. Today, promethium (Pm-147), with a half-life of 2.4 years, is used for this purpose. 

Fig. 19 Dependence of the brush thickness reduced by the number of polymer repeat units for monovalent co-ions, H/AT, on the concentration of the external salt, ( s> for strong (solid line) and weak (dashed line) polyelectrolyte brushes in neutral brush (NB), salted brush (SB), and osmotic brush (OB) regimes, a and ao denote the bulk and internal (for weak polyelectrolyte brushes only) degree of dissociation, respectively (Reproduced with permission from [89])...

If salt is present in the solution, counterions as well as co-ions do penetrate into the brush, which leads to additional screening of the Coulomb repulsion inside the brush. The amount of this screening, and the stretching of the polyelectrolyte chains, are now also controlled by the bulk salt concentration. Since the additional salt screening weakens the swelling of the brush caused by the counterion osmotic pressure, salt leads to a brush con-... 

The threshold salt concentration above which the brush contraction sets in is given by the salt concentration which equals the counterion concentration inside the brush. This means that the higher the grafting density (and consequently the higher the internal counterion concentration in the osmotic brush regime), the larger the salt concentration necessary to see any salt effects at all. 

Yoshizawa, M. and Ohno, H., Molecular brush having molten salt domain for fast ion conduction, Chem. Lett., 889,1999. 

Sulfamic acid has a unique combination of properties that makes it particularly well suited for scale removal and chemical cleaning operations, the main commercial applications. Sulfamic acid is also used in sulfation reactions, pH adjustment, preparation of synthetic sweeteners (qv), and a variety of chemical processing applications. Salts of sulfamic acid are used in electroplating (qv) and electroforming operations as well as for manufacturing flame retardants (qv) and weed and brush killers (see Herbicides). 

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