Use Of Nitric Acid Research Articles

319 Reflections on the most cited paper in the ninety-nine-year history of Canadian Society of Animal Science

Abstract Measurement of nutrient digestibility is a key pillar in estimating the value of feeds for livestock. Conditions are not always amendable to estimating feed digestibility through total collection methods, and as a result digestibility markers are frequently employed. The first “Digestibility markers” were reported in the early 1900s where colored glass beads were used to estimate the flow of digesta through the digestive tract. Subsequently, a myriad of digestibility markers has been assessed with the internal markers; acid insoluble ash, acid detergent lignin, indigestible neutral detergent fiber and n-alkanes and the external markers titanium dioxide and chromic oxide being the most common. Chromic oxide (Cr2O3) was first proposed as a digestibility maker in 1918 and continues to be widely used in modern day metabolism, confined performance and grazing livestock experiments. It was the demand to use chromic acid as a digestibility marker that led Terry and Mira Fenton to publish the article “An improved procedure for the determination of chromic oxide in feed and feces” in the Canadian Journal of Animal Science in 1979. This became the most cited article in the history of the journal with over 800 citations. The procedure eliminated the use of nitric acid in a pre-digestion step and ashing reduced the organic matter content, making it less likely that perchloric acid would be converted to anhydrous perchloric acid which poses an explosive hazard. The procedure continues to be widely used to measure Cr2O3 as a digestibility marker and has made a significant contribution to our assessment of the value of a wide range of feeds for Canadian livestock.

Inorganic arsenic in seaweed: a fast HPLC-ICP-MS method without coelution of arsenosugars.

Seaweed is becoming increasingly popular in the Western diet as consumers opt for more sustainable food sources. However, seaweed is known to accumulate high levels of arsenic-which may be in the form of carcinogenic inorganic arsenic (iAs). Here we propose a fast method for the routine measurement of iAs in seaweed using HPLC-ICP-MS without coelution of arsenosugars that may complicate quantification. The developed method was optimised using design of experiments (DOE) and tested on a range of reference materials including TORT-3 (0.36 ± 0.03 mg kg-1), DORM-5 (0.02 ± 0.003 mg kg-1), and DOLT-5 (0.07 ± 0.007 mg kg-1). The use of nitric acid in the extraction solution allowed for the successful removal of interferences from arsenosugars by causing degradation to an unretained arsenosugar species, and a recovery of 99 ± 9% was obtained for iAs in Hijiki 7405-b when compared with the certified value. The method was found to be suitable for high-throughput analysis of iAs in a range of food and feed matrices including Asparagopsis taxiformis seaweed, grass silage, and insect proteins, and offers a cost-effective, fast, and robust option for routine analysis that requires minimal sample preparation. The method may be limited with regards to the quantification of dimethylarsenate (DMA) in seaweed, as the acidic extraction may lead to overestimation of this analyte by causing degradation of lipid species that are typically more abundant in seaweed than other marine matrices (i.e. arsenophospholipids). However, the concentrations of DMA quantified using this method may provide a better estimation with regard to exposure after ingestion and subsequent digestion of seaweed.

Ultrasound-assisted electrodialytic separation of cobalt from tungsten carbide scrap powder

Recycling of tungsten carbide-cobalt (WC–Co) will considerably grow in the future. Thus, efficient and greener methods for the recovery of the critical raw materials, Co and W, will be necessary. In this work, we evaluate the separation of Co from WC using an electrodialytic (ED) process alone and coupled with ultrasound-assisted extraction (UAE). The WC-Co powder was suspended in different leaching agents, and the effects of UAE amplitude (probe system), pulse periods, and treatment time were evaluated. The Co extraction was mainly dependent on the leaching agent when only UAE was applied, being more efficient under acidic pH. The ED process, alone and coupled to UAE, was then applied using a reactor with two compartments separated by a cation exchange membrane with nitric acid as anolyte; and the effect of DC intensity was tested for Co separation from WC. Between 24 % and 58 % of Co were solubilized when ED was applied alone, but these values increased up to 96 % through the combination with UAE. The ED process was also applied without the use of nitric acid, taking advantage of the acid generated through water electrolysis, aiming for a more environmentally friendly process. The best Co selective recovery was achieved when ED-UAE was used, reaching 99 % of Co solubilization and 90 % of the total Co electromigration to the cathode compartment, leaving behind the WC residue at the anode. The ED-UAE process presents as a greener process for Co separation from WC residues, with further tests needed to include W recovery.

Exploring the Remarkably High Photocatalytic Efficiency of Ultra-Thin Porous Graphitic Carbon Nitride Nanosheets.

Graphitic carbon nitride (g-C3N4) is a metal-free photocatalyst used for visible-driven hydrogen production, CO2 reduction, and organic pollutant degradation. In addition to the most attractive feature of visible photoactivity, its other benefits include thermal and photochemical stability, cost-effectiveness, and simple and easy-scale-up synthesis. However, its performance is still limited due to its low absorption at longer wavelengths in the visible range, and high charge recombination. In addition, the exfoliated nanosheets easily aggregate, causing the reduction in specific surface area, and thus its photoactivity. Herein, we propose the use of ultra-thin porous g-C3N4 nanosheets to overcome these limitations and improve its photocatalytic performance. Through the optimization of a novel multi-step synthetic protocol, based on an initial thermal treatment, the use of nitric acid (HNO3), and an ultrasonication step, we were able to obtain very thin and well-tuned material that yielded exceptional photodegradation performance of methyl orange (MO) under visible light irradiation, without the need for any co-catalyst. About 96% of MO was degraded in as short as 30 min, achieving a normalized apparent reaction rate constant (k) of 1.1 × 10-2 min-1mg-1. This represents the highest k value ever reported using C3N4-based photocatalysts for MO degradation, based on our thorough literature search. Ultrasonication in acid not only prevents agglomeration of g-C3N4 nanosheets but also tunes pore size distribution and plays a key role in this achievement. We also studied their performance in a photocatalytic hydrogen evolution reaction (HER), achieving a production of 1842 µmol h-1 g-1. Through a profound analysis of all the samples' structure, morphology, and optical properties, we provide physical insight into the improved performance of our optimized porous g-C3N4 sample for both photocatalytic reactions. This research may serve as a guide for improving the photocatalytic activity of porous two-dimensional (2D) semiconductors under visible light irradiation.

Energy saving Chemical Beneficiation Method of Improving Low Grade Nigeria Chromite Ore for Use in Steel Industries

This study detailed how direct acid leaching can be used to extract high grade chromite from low grade chromite ore for utilization in the steel industry. The suggested method, which makes use of nitric acid, avoids using traditional pyrometallurgical processes because they use a lot of energy. The leaching procedure is adjusted in accordance with the circumstances that will maximize chromium recovery. In this context, the independent variables are the nitric acid concentration (0.5–4 M), temperature (28–80°C), liquid to solid ratio (L/S) (3–10 mL g–1), and leaching period (10–120 min). The three parameters that affect the leaching process most effectively are, in order, acid concentrations, temperature, and particle sizes. By doing this, 86.7% of the chromite in the lean chromite ore was recovered. Shirking core model examination of the kinetics of leaching reveals that internal diffusion reaction controls the rate of leaching, and the apparent activation energy calculated is 24.8 kJ.mol-1. This approach is successful and relatively inexpensive for chromite beneficiation. The gap is thus filled by the use of all-known inefficient acid dissolution procedures, which are less expensive and could serve as an alternate way of chromite beneficiation for use in iron and steel.

A systematic review and meta-analysis of validated analytical techniques for the determination of total selenium in foods and beverages.

The intricate balance between the beneficial and harmful effects of selenium (Se) intake means that its quantification in food needs to be done correctly. Therefore, in this review, we systematized 105 articles to identify the most studied methodologies, analytical techniques, and food matrices. Among the analytical techniques employed, inductively coupled plasma mass spectrometry (ICP-MS) (n=29) emerged as the most commonly used method. The most prevalent hydrolysis methodology to digest Se in food matrices involved the use of nitric acid combined with ultrasound, which improved both the yield and digestion time. Optimal recovery values were achieved when total Se quantification accounted for the sum of Se(IV) and Se(VI) (94.4-99.4%) and for SeCys (88-96.5%). These findings are relevant for advancing methodological approaches, and their results emphasize the importance of developing alternative, faster, and lower-cost protocols for Se quantification in foods and beverages.

Kajian Siklus Daur Hidup pada Proses Produksi Industri Stainless Steel Gresik

“Gresik Stainless Steel Industry is one of the largest stainless steel factories in Indonesia since 1996 until now. With a sufficiently large production capacity, it is possible for the production process to produce emissions/by-products that can pollute the environment. This study approaches the production process of the Gresik Stainless Steel Industry using the Life Cycle Assessment (LCA) method. The scope of this research is gate to gate or during the stainless steel production process from the entry of materials to the release of finished products which include operating units from Coil Preparation Line Units, Coil Grinding Line Units, Mill Units, Annealing Pickling Line Units, Skinpass Units, Slitter Units , to Cut-To-Length Units. Life cycle assessment is carried out using the midpoint approach of the TRACI 2.1 method. Based on the results of the analysis, the APL unit is the operating unit that has the greatest influence on the eutrophication impact which has a total normalized value of 5025.309. This is due to the use of nitric acid as the main ingredient in the acidification process for the stainless steel production process.”

CHEMICAL MODIFICATION OF BITUMEN FOR STABLE ROAD CONSTRUCTION

Nitric acid has been found to be an effective additive for bitumen modification to enhance its performance and make it more appropriate for road construction purposes. This paper aims to provide an overview of the effects of nitric acid on bitumen properties, its application in road construction, and the benefits it offers. The paper explores the various methods of modifying bitumen with nitric acid, such as pre-treatment of bitumen, addition during mixing, and surface treatment of aggregates. The effects of nitric acid on the properties of bitumen, such as viscosity and stability, are discussed. Nitric acid improves the adhesion of the bitumen to the aggregates, enhancing the mixture of asphalt and aggregates, leading to improved stability and durability of the road surface. The paper also highlights the potential benefits of using nitric acid in road construction with bitumen. These benefits include improved resistance to moisture and temperature variations, reduced deformation under heavy loads, increased rutting resistance, and longevity of the bitumen pavement. The use of nitric acid with bitumen also facilitates the use of recycled bitumen products, which is more environmentally sustainable.

Assessment of the Health Risk of Indigenous People by the Consumption of Fish with Hg and As in Villages Located Close to Mining

The Amazon suffers from the occurrence of mining along its hydrographic routes, which releases toxic substances into the aquatic environment. The objective of this study was to evaluate the risk of contamination by As and Hg that indigenous peoples are exposed to through the consumption of fish in an area impacted by mining activity in the basin of the Curuá and Baú Rivers, Altamira-PA. In total, 55 fish specimens and 30 surface water samples were collected. The decomposition of the fish samples was done by wet method with the use of nitric acid, hydrogen peroxide, and microwaves. The quantification of total mercury (THg) and total arsenic (TAs) was carried out by inductively coupled plasma optical emission spectrometry with vapor generation (VG-ICP OES). The methodology proposed by the U.S. Environmental Protection Agency was used. The results showed that TAs presents safe levels; however, THg presents a sample with levels up to (4.6 µg g-1), exceeding the permitted levels (1 µg g-1). The risk assessment shows that only the consumption of fish, linked to Hg, represents the existence of deleterious risks to indigenous peoples (hazard quotient (HQ)) > 1). Bioaccumulation factor (BAF) in fish represents a risk to indigenous people, because of the Hg’s presence. The study identified that illegal mining activities are responsible for Hg pollution in the Baú and Curuá Rivers. The fish species analyzed can be used as bioindicators of Hg in the rivers, which is relevant for making environmental and public health policy decisions.

Nitric acid and hydrogen peroxide in the digestion of milk and cheeses for the detection of heavy metals

The content of arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb) and zinc (Zn) in milk and cheeses was determined, comparing the use of nitric acid and a mixture of nitric acid and hydrogen peroxide (HNO3 + H2O2) in acid digestion. The milk was collected from storage tanks in localities of Huejotzingo and cheeses in Santa Ana Xalmimilulco, Huejotzingo, Puebla. Digestion was carried out in a CEM MarsX microwave. The determination was in an ICP OES. As it showed (p <0.01) when using HNO3 (0.13 mg kg-1) with respect to the mixture. The Cd, Zn and Pb showed (p <0.01), with the use of the mixture with respect to HNO3. The content of Cd, As, Cu and Cr in the cheese there was difference (p <0.01) when using HNO3 compared to the mixture. This shows that there is specificity for metal detection, with HNO3 being the most efficient

Technical Note: Methodology Development to Study Two-Dimensional Stainless Steel Pitting Corrosion Mechanisms Using Foil Samples

In this Technical Note, four foil sample preparation methodologies were investigated with “sandwich” like foil electrodes, which enabled the visualization of two-dimensional pit morphologies. The new procedure included the use of nitric acid to prepassivate the foil as the first step; polishing the top layer of the side edges of the foil after the foil was sandwiched in between two glass slides; and immersing the corners in nitric acid before experiments. This new foil sample preparation methodology eliminated pitting artifacts at the corners of the foil samples and provided reliable and reproducible experimental results.

ДОСЛІДЖЕННЯ ПРОЦЕСУ НІТРАТНОКИСЛОТНОЇ ПЕРЕРОБКИ ФОСФОГІПСУ З ОДЕРЖАННЯМ КОНЦЕНТРАТУ РІДКІСНОЗЕМЕЛЬНИХ ЕЛЕМЕНТІВ

Investigate the process of extraction of rare earth elements from phosphogypsum by its interaction with nitric acid, concentration 25, 30 and 35%, at a ratio of "phosphogypsum: acid" 1: 2 and a temperature of 700C to obtain purified calcium sulfate. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained. Experimental studies were performed using the titrimetric method using Trilon B to determine the concentration of rare earth elements in the obtained filtrates. A review of scientific and technical literature in the field of promising methods of processing phosphogypsum. The most alternative method of processing phosphogypsum is to obtain rare earth elements by acid leaching, which is provided by the use of mineral acids. Based on the obtained data, it was found that when the acid concentration increases from 25 to 35%, the content of rare earth elements (REE) in the filtrates of the samples increases from 0.21 to 1.68 g/dm3, respectively. It was found that the degree of extraction of REE concentrate from phosphogypsum is highest at an acid concentration of 25% and is 22.8%, and with increasing concentration of HNO3, it decreases by almost 2.5 times. The optimal concentration of the nitric acid solution was determined, which is 25% and interacts with phosphogypsum for the subsequent extraction of the precipitate of rare earth elements.The optimal temperature of nitric acid processing of phosphogypsum, which is 70 0C, was revealed. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained.The use of nitric acid for the production of rare earth elements from phosphogypsum and for the production of purified phosphogypsum sediment from soluble impurities scientifically substantiated. The content of rare earth elements in the filtrate was determined at various acid concentrations. The efficiency of sediment removal of rare earth elements from phosphogypsum by interaction with nitric acid at a concentration of 25, 30 and 35%, respectively, was established. Purified phosphogypsum can then be used to produce gypsum binder in the construction industry and in fertilizer technology in agriculture. Concentrate of rare earth elements can be used in medicine, metallurgy and other industries with the selection of individual elements and in general.

Simulation of non-stationary operating modes of ammonia oxidation reactor in the process of nitrogen acid production

The use of nitric acid in various branches of chemical production leads to an increase in the demand for the production itself and the economic efficiency of the process. At the moment, many methods for obtaining nitric acid are known. The article considers a method of contact oxidation of ammonia on a platinum-rhodium catalyst, followed by nitrogen release for absorption. Ammonia oxidation is performed using various technologies, in particular, by continuous oxidation in a sectional catalytic reactor based on a platinum-rhodium catalyst.To automatically control a three-section reactor, you need to know the mechanisms of interaction of an ammonia-air mixture (APS) with a platinum-rhodium catalyst. A mathematical model that is adequate to the actual course of the oxidation process will ensure high management efficiency by meeting the quality requirements of the initial product and reducing the economic costs of nitric acid production.It is important to create a mathematical model of the Reactor space in the contact layer, which would give an adequate reflection of the behavior of the catalyst in it when changing the properties of the ammonia-air mixture and the reaction volume continuously entering the reactor. Well-known modern modeling methods use generalized analysis of the input substance and are based on an approximation of experimental data on the nature of the oxidation process. In the article, a mathematical model was formed that describes the behavior of the reaction space in the reactor, taking into account non-stationary conditions, the course of the process.It is proposed to consider a reactor with three contact layers, each layer as separate objects with separate reaction contact zones. The reaction volume in the reactor is formed as a set of reaction spaces, contact layers with the contact flow. The properties of the catalyst, which is located in the contact layer, change dynamically as a result of the manifestation of non-stationary flow of the process over time.The oxidation reactor is considered as a phenomenon that involves the presence of countless random microprocessors. This verbal model made it possible to determine the methods of mathematical modeling that should be used when creating a model for the control system. The developed model gives an idea of the relationship between the ammonia-air mixture and the catalyst. Get the transfer functions for the channel with the input coordinate of the ammonia-air ratio and the channel with the input coordinate of the mixture temperature.

Microwave-Assisted Degradation of Biomass with the Use of Acid Catalysis

The aim of the study was to assess the effectiveness of microwave pretreatment combined with acid catalysis in the decomposition of various types of biomass (pine and beech chips and hemp stems). It was clearly demonstrated that sulfuric acid was a catalyst enabling the most effective decomposition of the tested plant biomass, guaranteeing the highest concentrations of simple sugars released. Acid catalysis with 1% v/v sulfuric acid combined with microwave radiation provided high glucose concentrations of 89.8 ± 3.4, 170.4 ± 2.4 and 164.6 ± 4.6 mg/g for pine chips, beech chips and hemp stems, respectively. In turn, the use of nitric acid promoted the degradation of hemicellulose, which resulted in high concentrations of galactose and xylose, i.e., 147.6 ± 0.6, 163.6 ± 0.4 and 134.9 ± 0.8 mg/g of pine chips, beech chips and hemp stems, respectively, while glucose levels remained relatively low. It was also demonstrated that the undesirable dehydration of sugars such as glucose and xylose is more pronounced in sulfuric acid than nitric acid processes. The use of H2SO4 and increased pressure generated 5-hydroxymethylfurfural (5-HMF) and furfural at a concentration of ca. 12 and 6 mg/g, 10 and 45 mg/g and 14 and 30 mg/g, of pine chips, beech chips and hemp shoots, respectively. Our studies confirmed the usefulness of the combined use of microwaves and acid catalysis in the degradation of softwood, hardwood and non-wood plant biomass. It should be emphasized that obtaining high concentrations of released simple sugars (as potential substrates in biosynthesis), while maintaining low levels of toxic by-products (inhibitors), requires precise selection of process parameters such as pressure, exposition time and type of acid catalyst.

Evaluación comparativa de tratamiento a base de ácidos y bases sobre el sierro para la sacarificación mejorada con celulasas termófilas

The present study focuses on the use of thermophilic recombinant cellulases to produce fermentable sugars for conversion to bioethanol which is an important renewable energy resource to be worked upon due to climatic change, energy insecurity and nonrenewable nature of fossil fuels. Therefore, sawdust of pinus wood was subjected to pretreatment using different acids such as phosphoric, nitric, acetic and alkalis i.e. sodium hydroxide, calcium hydroxide and ammonia in various concentrations. Maximum delignification was observed using 8% nitric acid as it resulted in to 74.02% delignification and increased the cellulose availability to 81.8%. Subsequently, pretreated biomass was assessed for improvement in hydrolysis to less complex sugars employing thermophilic recombinant cellulases cloned from Thermotoga petrophila. Saccharification reaction parameters such as Incubation time, temperature, biomass and enzyme concentrations were optimized. The optimized conditions were revealed as 3 h incubation time, 65℃ temperature 0.1 % (w/v) substrate, 250, 2550 and 70140 U of Endo-1,4-β-glucanase, Exo-1,4-β-glucanase and β-1,4-Glucosidase, respectively. This optimization study resulted in 34.61% saccharification yield which is 1.82 folds increase compared to saccharification yield of untreated biomass. This study is unique in providing insight to pretreatment using Nitric acid as in literature use of nitric acid as a pretreatment agent is not well investigated.

Highly dispersed metal incorporated hexagonal mesoporous silicates for catalytic cyclohexanone oxidation to adipic acid

Abstract Adipic acid is a dicarboxylic acid of great industrial importance, mainly used in the production of nylon-6,6 and polyurethane. The use of nitric acid as an oxidant in the industrial production of adipic acid poses significant carbon footprint to the environment. Clean adipic acid synthesis methods using a heterogeneous catalyst with H2O2 as oxidant and water as solvent have potential advantages of low catalyst cost, easy synthesis and recovery, cleanness and environmental protection. In this work, hexagonal mesoporous silicate materials were synthesized by a sol–gel method and evaluated for cyclohexanol/cyclohexanone oxidation to adipic acid. The physical and chemical properties of Fe-HMS were characterized by XRD, HR-TEM, BET and UV–Vis. The experimental results showed that Fe-HMS materials show pore sizes ranging from 2–3 nm. W- and Mo-based polyoxometalates were also evaluated and compared to the Fe-based HMS catalysts. To improve the adipic acid yield, the influence of the transition metal as well as the effect of metal loading, reaction temperature and catalyst amount on the catalytic performances of Fe-HMS have been investigated in details. When Si/Fe atomic ratio = 100, Fe-HMS catalyst shows the highest activity, with a cyclohexanone conversion of 92.3% and adipic acid selectivity of 29.4%. The reaction pathway of cyclohexanone oxidation was further proposed based on experimental data.

Use of Nitric Acid to Control the NO <sub>2</sub> :NO <sub>X</sub> Ratio within the Exhaust Composition Transient Operation Laboratory Exhaust Stream

<div class="section abstract"><div class="htmlview paragraph">The Exhaust Composition Transient Operation Laboratory<sup>TM</sup> (ECTO-Lab<sup>TM</sup>) is a burner system developed at Southwest Research Institute (SwRI) for simulation of IC engine exhaust. The current system design requires metering and combustion of nitromethane in conjunction with the primary fuel source as the means of NO<sub>X</sub> generation. While this method affords highly tunable NO<sub>X</sub> concentrations even over transient cycles, no method is currently in place for dictating the speciation of nitric oxide (NO) and nitrogen dioxide (NO<sub>2</sub>) that constitute the NO<sub>X</sub> mixture. NO<sub>X</sub> generated through combustion of nitromethane is dominated by NO, and generally results in an NO<sub>2</sub>:NO<sub>X</sub> ratio of < 5 %. Generation of any appreciable quantities of NO<sub>2</sub> is therefore dependent on an oxidation catalyst to oxidize a fraction of the NO to NO<sub>2</sub>. Presented within this manuscript is a method for precise control of the NO<sub>2</sub>:NO<sub>X</sub> ratio within the ECTO-Lab exhaust stream by using nitric acid as the NO<sub>X</sub> precursor molecule in lieu of nitromethane. While decomposition of nitromethane generates NO as the dominate component of the NO<sub>X</sub> mixture, nitric acid decomposition produces primarily NO<sub>2</sub>. The method described herein entails metering a 70 % aqueous nitric acid solution into an upstream decomposition furnace prior to injection into the ECTO-lab exhaust. By use of nitric acid as the precursor NO<sub>X</sub> molecule, and precisely controlling the conditions at which decomposition of nitric acid occurs, the ECTO-Lab may be used as a platform to evaluate catalytic activity in absence of a diesel oxidation DOC, coming one step closer to a full engine simulator. In this study, concentrations of NO<sub>2</sub> well in excess of the theoretical thermodynamic equilibrium value were achieved by specifying the residence time and temperature of the nitric acid within the decomposition oven.</div></div>

Process optimization of the destruction of polymer binding in solid propellants with the use of nitric acid

Process optimization of the destruction of polymer binding in solid propellants with the use of nitric acid

Recent Advances on the Analysis of Polychrome Works of Art: SERS of Synthetic Colorants and Their Mixtures With Natural Dyes.

The development and application of proper sample pretreatments is often a key step toward the successful analysis of dyes used as artists' materials by surface-enhanced Raman spectroscopy (SERS). Complexation of the organic colorants with metal ions to dye fabrics and produce lake pigments, as well as undesired interactions with other matrix components such as substrate, binding media, fillers, and extenders, are just some of the issues that typically complicate dye identification in minute samples from invaluable artworks and museum objects. These concerns may be addressed by using, prior to SERS analysis, ad-hoc sample pretreatments that, in addition to increasing the technique's sensitivity, favorably affect its selectivity toward certain molecules or molecular classes. The present work describes a newly developed sample pretreatment based on the use of nitric acid that has proven crucial for the successful detection of aniline and xanthene dyes–the first synthetic organic colorants to be used in printing and painting, among other art forms–in microscopic samples from works of art such as a 19th-century silk fabric, paper cut-outs by Henri Matisse, Vincent Van Gogh's Irises, and Japanese woodblock prints. This treatment promotes the hydrolysis of the dye-metal bond in mordant dyes or lake pigments, resulting in a more efficient adsorption of the dye molecules on the SERS-active substrate and, hence, enabling the acquisition of high-quality spectra. In the case of synthetic colorants, this method shows advantages over hydrolysis with hydrofluoric acid–a procedure previously established for the analysis of red lakes prepared from natural dyes. The nitric acid treatment presented here may be integrated into a multi-step methodology that, by exploiting differences in solubility of various dyes and lake pigments, has enabled for the first time to successfully characterize intentional mixtures of natural and synthetic colorants of the xanthene and anthraquinone molecular classes, i.e., eosin Y and carmine, in a selection of Japanese prints of the Meiji era. The present study paves the way for the systematic identification of synthetic dyes in objects of artistic and archeological interest, even when they are present in mixtures with natural organic colorants.

Effect of potassium fertilizer, either KNO3, K2SO4 or KCl, in a saline fertigation solution on the growth of Medjool date palm plants pot-grown in river sand or river sand/calcium carbonate

A pot trial was carried out to assess the effect of three fertigation nutrient mixtures on the growth of Medjool date palm plants. The plants were grown either in river sand or in a 20% calcium carbonate - 80% river sand mixture to approximate desert soil conditions. Each fertigation solution comprised all of the elements required for healthy growth. The source of potassium of each solution differed. The fertilizer sources for the nutrients besides potassium were the same. The nitrate to ammonium ratio was markedly greater in the solution made up using KNO(3). The concentration of each element in each solution was identical, except for a relatively small increase in the SO(4)(2-) concentration in the solution made up with K2SO(4) and a relatively small increase in Cl- concentration in the solution make up with KCl. These differences were unavoidable, being a consequence of the K source used. In addition, an equal amount of NaCl was added to each solution to render the solutions saline. The plants were fertigated three times a week. Growth was assessed in terms of plant height on a number of dates after planting, and top leaf-stem fresh weight, root fresh weight, number of compound leaves, or number of primary roots when the plants were lifted from the pots, two years after planting. The plants grew better in the sand-calcium carbonate mixture. No interaction was apparent with respect to medium type and fertigation solution. The plants fertigated with the solution made up with KNO(3) grew better than those fertigated with the solution made up with KCl or K2SO(4). They were of greatest height and showed prominence in the other growth parameters assessed. A difference in growth relating to whether KCl or K2SO(4) was the K source was not clearly apparent. It was concluded that the growth of Medjool date palm plants could be expected to be better when nitrate predominates over ammonium in applying fertilizers. To maximize nitrate in a fertigation solution or fertilizer mix, the obvious option available is to use KNO(3) as the K source in endeavoring to match solution nutrient concentrations with date palm nutrient demand. The use of nitric acid can also be considered.