Additive effects brightening

The instability of DAST-type brighteners towards chlorine-containing bleaches has been mentioned already. They also show limited stability towards per-acids. As recommended washing temperatures have tended to fall in recent years, a bleach consisting of sodium perborate activated by addition of tetra-acetylethylenediamine (11.63) has become an important component of household detergent formulations. This system is effective at temperatures as low as 40-50 °C. Since the FBA may be sensitive to the activated oxidant, however, in some formulations it is necessary to protect compounds such as 11.60 or 11.61 by encapsulating either the brightener or the activator, if adequate shelf-life is to be maintained. 

Additives can be consumed at the cathode by incorporation into the deposit and/or by electrochemical reaction at the cathode or anode. Consumption of coumarin in the deposition of nickel from a Watts-type solution has been studied extensively. Thus, in this section we discuss the consumption of coumarin, which is used as a leveler and partial brightener. In a series of papers (33, 36), Rogers and Taylor, described the effects of coumarin on the electrodeposition of nickel. They found that the coumarin concentration decreases linearly with time at —960 mV (versus SCE and 485 to 223 rpm at a rotating-disk electrode, for plating times of 8 to 75 min. A rotating-disk electrode was used to achieve a uniform and known rate of transport of additive to the cathode. Rogers and Taylor found that the rate of coumarin consumption is a function of coumarin bulk concentration. Figure 10.16 shows that the rate of consumption... 

Objects are painted for many reasons to prevent rusting and deterioration, to make them attractive, to evoke emotions, and to brighten our lives. Wagons are painted with these goals in mind. An artist has the same goals permanence, attractiveness, and emotional effect in addition, an artist paints a work of art to preserve the past. 

If the solubility of inorganic salts in the chosen medium is low, complexing additives are used [174,185] which apparently also exert a brightening effect. 

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