Citric acid, additive

Table 12.26 Effect of citric acid addition on the composition of cane sugar after hydrolysis [211]...

The microstructure of the hardened paste was investigated as a function of the citric acid addition by... 

In the present research work the addition of citric acid did not cause any change in the solubility of the hemihydrate. But with an equal water/gypsum ratio a decrease of the viscosity was observed with increased citric acid addition. 

The alterations can be partly derived from Fig. 2. The figure shows the measured increase of the average circumferences U and areas F, and the decrease of the shape factor K and of the texture index Q above increased citric acid additions. More details of the experimental data are given elesewhere [2]. 

The rate of hydration also causes changes in the microstructure. A slow rate causes a more distinct change toward a compact crystal shape. Citric acid addition causes a decrease in the total porosity and an increase in the average pore diameter. As a result gypsum strength was found to decrease with increasing additions of citric acid. 

One possible solution to the lack of enantioselectivity observed with citric acid additive is the addition of a chiral amino alcohol (eq 28), which performs the same chelating role as the citrate and locks the reaction into the second cycle. However, the chiral backbone of the ligand is then capable of imparting enantioselectivity during a subsequent dihydroxylation reaction. While this area clearly has much potential for development, the enantiose-lectivities obtained are not yet competitive with those commonly realized with the conventional AD process. 

Ferrous salts are easily oxidised in solution into the inactive ferric salts. This can be inhibited by complex formation with citric acid, addition of reducing sugars, reducing the amount of air oxygen by completely filling of the bottles and by exposing to light. 

Workman DS, Morris JR (1992) Storage stability on wine coolers as influenced by juice content and citric acid addition. J Food Qual 15 39-52... 

The effect of citric acid addition is depicted in Fig. 19e. The first and second peaks, corresponding to the dissolution of mineral compounds and the formation of C-A-H, were less intense and shifted to a later stage. The third peak, due to monosulfoaluminate and ettringite, was shifted to an earlier stage proportionally to the amount of eitrie aeid addition. The fourth peak, corresponding to active C3S hydration, was shifted to a later stage. The shift was dependent on the amount of eitrie aeid added. 

Yamaguchi, L, lizuka, S., Osaka, A., Monma, H., Tanaka, J., 2003. The effect of citric acid addition on chitosan/hydroxyapatite composites. Colloids and Surfaces A Physicochemical and Engineering Aspects 214 (1-3), 111-118. 

Catalytic activity tests (Table 2) show that citric acid addition in NiMo/SBA-15 catalysts leads to an increase in the activity in DBT HDS and selectivity towards the direct desulfurization (DDS) route of the reaction. A comparison of the catalytic behavior of the NiMoCA/SBA-15 catalysts prepared by coimpregnation (C) and successive impregnation (S) methods indicates that the catalyst prepared by the C method resulted to be more active and more selective for the DDS route than its counterpart prepared by the S procedure. In general, activity and selectivity trends... 

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