Coating Metals with Zinc and Method for Measuring the Thickness of the Layer

2021 ◽  
Vol 30 (5) ◽  
pp. 443-453
Author(s):  
Miroslav Minchev ◽  
Keyword(s):  
Thin Layer ◽  
Zinc Salt ◽  
Copper Coin ◽  
The Relationship

When a copper coin is immersed with zinc into a solution of a zinc salt (ZnSO4, ZnCl2 etc.) an electrochemical eaction occurs in the mixture. As a result, a thin layer of zinc appears on the surface of the copper which gives the impression for silver color. The purposes of this project are: to explain the phenomenon and to investigate relevant parameters; to measure the thickness of the zinc layer; to determine which metals can be covered with zinc in such experiments. Method for measuring the thickness of the zinc layer was obtained by using dimension properties of the coin – radius, height and mass. The advantage of this method is the fact that it can be applied for all metals whose form has an integrable volume. The thickness of the layer was determined to be in the order of 1 . The relationship between the thickness of the zinc and the time at which the coin has spent in the solution was also studied and an exponential tendency was observed. It was proved that only metals after hydrogen in the Reactivity series can be plated with zinc with this setup.

Evaluation of Reflectance Fluorodensitometry for Measuring Aflatoxins on Thin Layer Plates

1971 ◽  
Vol 54 (4) ◽  
pp. 870-873
Author(s):  
Walter A Pons
Keyword(s):  
Thin Layer ◽  
Silica Gel ◽  
Uv Light ◽  
Plate Surface ◽  
Coefficients Of Variation ◽  
Standard Application ◽  
Tlc Plates ◽  
Relationship Of ◽  
The Relationship

Abstract A reflectance fluorodensitometer employing illumination of chromatograms with longwave UV light at 45° angles to the plate surface and measurement of reflected fluorescence at 90° was found to be suitable for measuring aflatoxins on silica gel-coated thin layer plates. The relationship of peak area vs. concentration was linear for 1–20 ng aflatoxins B1 and G1/ spot. Degradation of aflatoxins was slight. Five repetitive scans of the same chromatogram containing 5 ng each of B1 and G1 reduced the recorded areas an average of 1% per scan. Consecutive scans of 8 identical standard chromatograms containing 5 ng each of B1 and G1 and 1.5 ng each of B2 and G2 showed a reproducibility, as measured by coefficients of variation, of ±4–5% (B1 and G1) and ±5–9% (B2 and G2), representing the combined errors of standard application, TLC development, and scanning. Analysis of aflatoxins in purified sample extracts from 6 contaminated oilseed meals, 3–500 μg afla toxins/kg, in which the same TLC plates were scanned by a transmission densitometer and the reflectance densitometer yielded essentially equivalent values.

Serum Content of Macroglobulins (19S Fraction) and Its Variation with Age when Determined by Thin-Layer Gel-Filtration

1970 ◽  
Vol 16 (9) ◽  
pp. 740-742 ◽  
Author(s):  
Lleni Pach de Goldman ◽  
Liliana Ballivian ◽  
Ernesto Melgar
Keyword(s):  
Thin Layer ◽  
Total Protein ◽  
Healthy Subjects ◽  
Serum Proteins ◽  
Gel Filtration ◽  
Different Ages ◽  
The Relationship ◽  
Apparently Healthy

Abstract Serum proteins were fractionated by thin-layer gel-filtration on Sephadex G-200, and the content of macroglobulins (19S fraction) was determined in 137 samples from apparently healthy subjects of different ages. The relationship between amount of 19S fraction relative to total protein was found to vary widely with age. This variation has to be considered when the method is used for clinical purposes.

Relationship of basal plane and prismatic stacking faults in GaN to low temperature photoluminescence peaks at ∼3.4 eV and ∼3.2 eV

2004 ◽  
Vol 831 ◽  
Author(s):  
J. Bai ◽  
M. Dudley ◽  
L. Chen ◽  
B. J. Skromme ◽  
P. J. Hartlieb ◽  
...  
Keyword(s):  
Low Temperature ◽  
Thin Layer ◽  
Basal Plane ◽  
Stacking Faults ◽  
Structural Defects ◽  
Cubic Phase ◽  
Bulk Crystals ◽  
Relationship Of ◽  
The Relationship ◽  
Low Temperature Photoluminescence

ABSTRACTThe relationship between the optical properties and microstructure of GaN is of great interest due to the important optical and electronic applications of this material. Several different studies have been reported attempting to link the low temperature photoluminescence (PL) peak at ∼3.4 eV to the presence of various microstructural defects. However, no clear systematic studies have been reported establishing such a link for the PL peak observed at ∼3.2 eV. In this paper, we present evidence linking the ∼3.4 eV PL peak to the presence of a thin layer of cubic phase associated with basal plane stacking faults (BSF). This relationship is mainly established by studying a series of ammonothermally-grown GaN bulk crystals. The existence and strength of the ∼3.4 eV peak are found to be related to the I2 type BSF (RI2=1/3<1>) observed in these samples. To investigate the relationship between the ∼3.2 eV peak and structural defects, a series of GaN epilayers grown on either SiC or sapphire (of various off-cut angles) was investigated by TEM and PL spectroscopy. Samples grown on 3.5° off-cut SiC and 5° and 9° off-cut sapphire substrates exhibit PL peaks near ∼3.2 and ∼3.4 eV, which are absent in the on-axis SiC and sapphire cases. TEM shows that the former group of samples has defect configurations consisting of prismatic stacking faults (PSFs) folding back and forth between two different {1120} planes connected by stair rod dislocations, which in turn fold onto to I1 type BSFs again with stair rod dislocations at the fault intersections. The ∼3.2 eV PL peaks are proposed to possibly arise from transitions involving the PSFs and the stair rods associated with their mutual intersections and their intersections with the BSFs. The ∼3.4 eV peak is again attributed to the thin layer of cubic phase associated with the I1 type BSF (three bilayers as opposed to four bilayers for the I2 type BSF).

Colorimetric Determination of Carbofuran in Formulations

1978 ◽  
Vol 61 (6) ◽  
pp. 1513-1515
Author(s):  
Swadesh K Handa ◽  
Anand K Dikshit
Keyword(s):  
Thin Layer ◽  
Thin Layer Chromatography ◽  
Absorption Maximum ◽  
Colorimetric Determination ◽  
The Relationship ◽  
Layer Chromatography ◽  
Colored Compound

Abstract Carbofuran formulations are cleaned up by thin layer chromatography to separate possible interferences from carbofuran. Carbofuran phenol is reacted with vanillin to form a colored compound with an absorption maximum at 550 nm. The relationship between absorbance and concentration of carbofuran is linear from 5 to 50 μ5 ml solution. Recoveries of carbofuran from laboratory-prepared formulations ranged from 98.0 to 98.93%.

Assay of L( + )-Ascorbic Acid in Buttermilk by Densitometric Transmittance Measurement of the Dehydroascorbic Acid Osazone

1974 ◽  
Vol 57 (1) ◽  
pp. 65-69
Author(s):  
Paul R Beljaars ◽  
Wouter Van Steenbergen Horrocks ◽  
Theo M M Rondags
Keyword(s):  
Ascorbic Acid ◽  
Acetic Acid ◽  
Quantitative Analysis ◽  
Thin Layer ◽  
Coefficient Of Variation ◽  
Dehydroascorbic Acid ◽  
Tlc Plates ◽  
The Relationship ◽  
Layer Chromatography ◽  
Flying Spot

Abstract A study is presented for the quantitative analysis of ascorbic acid in buttermilk samples, using densitometric transmittance measurements. The procedure is based on oxidation of ascorbic acid to dehydroascorbic acid, followed by reaction with 2,4-dinitrophenylhydrazine to form the dinitrosazone. The osazone is separated from interfering substances in the sample by thin layer chromatography (TLC) on silica gel G plates developed with chloroform-ethyl acetate-acetic acid (60+35+5) . The TLC plates are scanned with a flying-spot densitometer. The relationship between integrated signal and concentration is linear for 0.08—1.00 fig ascorbic acid (coefficient of variation 3—4%). Deviations from Beer's law start to appear at levels higher than 1.00 fig ascorbic acid. A mean coefficient of variation of 3.5±1.1% (P = 95%) was established for standard spot measurements (3 spots averaged) on 15 chromatoplates. Recovery of ascorbic acid added to buttermik was 98% (coefficient of variation 7.2%). Results of this study are compared with those reported for spectrophotometric, titrimetric, and potentiometric procedures. The proposed method is less accurate because of interferences and the subsequent variables which arise as a result of taking transmittance measurements through an opaque medium.

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