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The Chemical Balance—From stones to electronics

2013-10-29T16:44:18Z

Title: The Chemical Balance—From stones to electronics Authors: Wisniak, Jaime Abstract: A chemical balance is standard equipment in any chemistry or physics laboratory, but in this electronic age a balance using weights is as odd as a slide rule. Weighing devices made their appearance at the time when human societies started to take root; the early devices were mechanical and developed very slowly until the seventeenth or eighteenth century when science started to· set its principles. The next two centuries saw the mechanical balance achieve its final shape until its replacement by electronic devices in the second part of the twentieth century. Here, the history of the development of the balance since the dawn of history until its final mechanical form in the second half of the nineteenth century is being traced. Page(s): 705-712

Reduction of bitter component of pomelo juice by chemical treatment and immobilized enzyme

2013-10-29T16:44:06Z

Title: Reduction of bitter component of pomelo juice by chemical treatment and immobilized enzyme Authors: Ghosh, U; Gangopadhyay, H Abstract: Effect of pH, total soluble solids (TSS), β-cyclodextrin, immobilized enzyme on removal of naringin and on quality of pomelo juice was studied. The maximum reduction in naringin content (0.34 mg/mL) was observed in juice, treated with immobilized naringinase compared to control (1.1mg/mL). Change of pH from 3.5 to 4.5 reduced naringin content from 31.8% (pH 3.5) to 40.9% (pH 4.5). However, lowering of bitter principle was 49% for 30°B and 43.6% for juice of pH 4.5 & TSS 30°B. Minimum changes in physicochemical parameters were observed with immobilized enzyme treated juice. Effect of these treatments on the activity of enzymes were also studied. Minimum amylase activity was observed with immobilized enzyme treated sample 18.9 U to that of control 32 U. Change in pectin methyl esterase (PME) activity was not so significant with an increase of pH. Maximum reduction of PME activity was observed with sample of 30°B TSS. However, retention of peroxidase activity was maximum for β-cyclodextrin treated sample 2.1 K₁×10³/mL compared to control 2.7 K₁×10³/mL. Treatment with immobilized enzyme gave an acceptable debittered pomelo juice. Page(s): 701-704

Studies on ionic mass transfer with insert helical tape promoters in batch fluidized beds

2013-11-03T16:42:39Z

Title: Studies on ionic mass transfer with insert helical tape promoters in batch fluidized beds Authors: Sujatha, V; Prasad, P Rajendra; Sarma, C Bhaskara; Raju, G J V Jagannadha Abstract: Augmentation of mass transfer coefficients, due to the presence of helical tape promoters in batch fluidized beds has been presented. Mass transfer coefficients have been evaluated from the measured limiting current densities and the concentrations of the reacting ions. The variables studied are the geometric parameters of the promoter-tape width, pitch and diameter of the promoter rod, the flow rate of the electrolyte, void fraction and particle diameter. It is found that k_L increased with increased flow rate and particle diameter. The increase in tape width and diameter of the promoter rod resulted in slightly increased mass transfer coefficients. Pitch of the promoter showed negligible effect on k_L. Page(s): 694-700

Kinetic and mechanistic studies of saponification of industrially important esters viz. diesters in alcohol-water and dioxane-water moieties—A novel mathematical approach for evaluation of concentrations of half-ester and end-products

2013-10-29T16:44:42Z

Title: Kinetic and mechanistic studies of saponification of industrially important esters viz. diesters in alcohol-water and dioxane-water moieties—A novel mathematical approach for evaluation of concentrations of half-ester and end-products Authors: Rao, B M; Gajanan, K; Rao, T Raghunath Abstract: Kinetic and mechanistic studies of saponification of seven structurally related and industrially important diesters have been investigated. These saponification processes were followed as series first order reactions and a novel mathematical approach of determinantal method of evaluation of concentrations of half-ester and other end products was applied. Time ratio method and Swain's standard data for series first order reactions have been utilized for the evaluation of rate data and thermodynamic parameters viz. ΔE^≠, -ΔH^≠, ΔG^≠, ΔS^≠ and logA for both the steps which involve the competitive and consecutive saponification reactions. Further, these reactions indicate that the first step of saponification process is much faster than the second step and the tau rates are more saponifiable than stearates and oleostearates. The concentrations of half-ester and end-products could not be monitored experimentally, however, they are evaluated through the application of the above said mathematical approach. The advantage of this novel mathematical approach is that the concentrations of half-ester and end-products thus evaluated are within the mathematical accuracy of ±0.005%. Page(s): 684-693