Acids - Science topic

Suggest reviewing the following paper:

Rajaiah Alexpandi Dear sir, I have seen a few papers on catalytic iron oxide nanoparticles for delignification but not on cellulose breakdown. Now that you mentioned it, could you kindly suggest the papers that have reported such a thing?

Here is a paper on Nyquist plot that was really helpful to me (Sensors 2021, 21(19), 6578; https://doi.org/10.3390/s21196578).

It explains most of what you asked for (except inhibition efficiency).

Hello Abdullah Al Ragib Abdullah Al Ragib,

there is already a question on the solubility of PET, which you can find here:

Maybe this can help you with your problem.

Try to mix the pectin thoroughly with a few drops of ethanol. When the ethanol has wetted the pectin, you can add water to dissolve it and make your desired solution.

Thanks for your answers! I will use an HCl bath (still deciding on the concentration to keep) and also soak new glassware in HCl, as we just got some.

You can use LiBr, Et3N and MeCN (containing 2 vol % of water) reaction conditions. These conditions allow room temperature hydrolysis to be carried out (15 min - 48h). This is the reference that related to:

But I don't know examples of application this method for dialkylmalonate substrates. If you try this, please share the results.

Do they still let you use cleaning solution? We made that in the lab, I believe from sulfuric acid and sodium dichromate. Nasty stuff, but it removes just about everything given a little time.

On the basic side KOH in alcohol does a good job on many things. Again, nasty stuff and it can etch glass, but not quartz.

Typical commodity pig feed in general does not need to be sterilized unless there are certain animal products in it. Acidifying the brewers yeast halts its growth which can be problematic during processing and storage, especially if it is mixed with fermentable sugars such as might be found in various grains. Also, some brewers feel their strains are highly proprietary and would want to prevent them from being easily cultured.

Formaldehyde might not be an allowable feed additive. As Martin noted, it would reduce its nutritional value, likely by forming undesirable adducts with the proteins.

We have a patent over this process in Brazil BR102012013327(B1) see at espacenet.com

ABSTRACT BR102012013327A2

CRYSTALLIZATION OF XYLITOL IN WATER-ETHANOL USING XYLITOL AND SILICA (NANOPARTICULATE) PYROGENIC AS SEED, belonging to the sector of saturated compounds having hydroxyl groups attached to acyclic carbon atoms, in the form of acyclic polyhydroxy alcohols, consists of a xylitol crystallization process contained in a water-ethanol mixture through crystallization induced by heterogeneous primary nucleation, having fumed silica (nanoparticulate) as seed. The field of application and objective of this invention consists in the recovery of xylitol obtained by any means of production, and the invention consists in the application or use of fumed silica (nanoparticulate) with crystals of 5 to 7 nm in the formation of crystals with heterogeneous nuclei, aiming at the more efficient crystallization of xylitol in saturated solution. In the process "CRYSTALIZATION OF XYLITOL IN WATER-ETHANOL USING XYLITOL AND (NANOPARTICULATE) PYROGENIC SILICA AS SEED", for nucleation, grains (nanometric) of fumed silica are used in the crystallization process by cooling, using the initial saturation temperature of xylitol and a cooling speed that facilitate the formation of xylitol crystals in the solution.

To determine whether Hypoglycin A is acidic or basic, we need to consider its chemical structure and any ionizable functional groups. Hypoglycin A has an amino group (NH2) and a carboxylic acid group (COOH) in its structure. The amino group can act as a base, while the carboxylic acid group can act as an acid. In summary, Hypoglycin A contains both acidic and basic functional groups, with the carboxylic acid group contributing to its overall acidity and the amino group contributing to its overall basicity.

The specific pH at which Hypoglycin A might be more acidic or basic depends on the conditions of the solution it's present in. The stability of Hypoglycin A depends on several factors, including pH, temperature, and other environmental conditions. To determine the specific pH range at which Hypoglycin A is most stable, experimental stability studies would be needed.

Other researchers may contribute to pH stability. I recommend you consult the scientific literature.

The standard curve bends because there is not enough of the detection reagent to bind to/react with the higher concentration of proteins. Beyond that, there is a linear phase (500-2000), which may be due to precipitation of the protein scattering light.

The usable part of the standard curve is the linear part in the lower concentration range (0-125).

No doubt, Salicylic acid is solid in nature and LHA is a derivatives of salicylic acid and is actually used as a liquid gel in a skincare which found in liquid form..

What is probenesic acid? If uric normal but feeling pain of Gout then what to do,?

The use of Fluorescence Resonance Energy Transfer (FRET) peptides for measurement of clinically important proteolytic enzymes.

Carmona AK, Juliano MA, Juliano L.An Acad Bras Cienc. 2009 Sep;81(3):381-92. doi: 10.1590/s0001-37652009000300005.PMID: 19722010 Free article. Review.

Hola, buenos días

Ante todo me alegra saber nuevamente de Ud.

Por otro lado, cualquier otra duda puede consultarme, me agrada el intercambio de experiencias con colegas de diferentes instituciones.

Le añado además que el trabajo con los ácidos orgánicos de cadena corta y larga es muy interesante, versátil y sobre todo muy útil.

Le refiero, que en septiembre próximo estaré impartiendo clases prácticas de cromatografía en la Facultad de Química de la Universidad de la Habana a alumnos del cuarto año de Licenciatura en Química.

Saludos cordiales

Lic. Luis E Jiménez Rodríguez, MC

Due to the effect of diffusion layer on its salt form

Doaa Eladl , You need to consider the chemistry of the system, but I found that a good excess of acetic acid works better than most of the traditional buffer systems for some cases of applying nanoparticles of iron..

When the animals die, they decompose, and their remains become sediment, trapping the stored carbon in layers that eventually turn into rock or minerals. Some of this sediment might form fossil fuels, such as coal, oil, or natural gas, which release carbon back into the atmosphere when the fuel is burned. When these organisms die, the carbon remains locked in their bodies. Decomposers are able to break down this material and release carbon back into the atmosphere and the cycle can begin again. Without decomposers, the carbon would remain locked in dead organisms and could only be released through combustion. At the end of the food chain, decomposers break down these molecules and return carbon and nitrogen to the soil and air. “Cover crops” like clover, beans and peas, planted after the main crop is harvested, help soils take in carbon year-round, and can be plowed under the ground as “green manure” that adds more carbon to the soil. Farmers can also do less intensive tilling.Soils play a key role in the carbon cycle by soaking up carbon from dead plant matter. Plants absorb CO2 from the atmosphere through photosynthesis and this is passed to the ground when dead roots and leaves decompose. Plants absorb CO2 from the atmosphere through the process of photosynthesis and use it to build their roots, stems or leaves. Carbon is mainly transferred into the soil through the release of organic compounds into the soil by plant roots or through the decay of plant material or soil organisms when they die. Through the process of photosynthesis, plants assimilate carbon and return some of it to the atmosphere through respiration. The carbon that remains as plant tissue is then consumed by animals or added to the soil as litter when plants die and decompose. Decaying organic matter produces H+ which is responsible for acidity. The carbon dioxide (CO2) produced by decaying organic matter reacts with water in the soil to form a weak acid called carbonic acid. This is the same acid that develops when CO2 in the atmosphere reacts with rain to form acid rain naturally. As soil organisms decompose organic matter, nutrients are converted into simpler, inorganic (mineral) forms that plants can easily use. This process, called mineralization, provides much of the nitrogen that plants need by converting it from organic forms. In general, pH values in the topsoil are lower because topsoil is rich in organic matter and the decomposition of organic matter will lead to the production of more organic acids, thus lowering pH of topsoil. Natural processes tend to acidify soils. Base-forming cations are leached from soils, carbonic acid is formed from carbon dioxide, plant roots excrete organic acids, and decomposition produces acidic products.

Dear Kiran Donthula ,

'there_will_not_be_water_molecule_splitting_in_Lead_acid_battery (LAB) as_electrolyte', because each one (half cell's) electrode should respect^[1] this (1.23 V vs SHE^[2], near 25^oC) blocking-drawback^[3,4] of the potential (vs SHE) .

However, an ideal aqueous electrolyte based supercapacitor (or an ideal LAB) might stretch/go up to: 2.46 V [= 1.23 V - (-1.23 V)], as a maximum cell voltage.

thank you very much. I will try your suggestion.

You could add small aliquots of moderately concentrated HCl while continuously mixing. However, if you are concerned about overshooting to a very low pH value, an alternative would be to add a buffer pH,d to the lowest acceptable pH value. For example, acetate pH 5 Could be used. If you want the final pH actually to reach 5, then acetate pH 4.5 would be more efficient. There would be some natural resistance to overshooting pH 5 because of acetate‘s pKa value.

Joshua Depiver thanks for the answer! In fact, I want to etch the Fe3O4 nanoparticles coated on the SiO2 wafer, but dissolving them should simply work too. I already started experimentation using milder acids (e.g. citric acid). I will try also your suggestion with stronger acids to see if that works.

Synthesising gelatin nanoparticles often involves complex processes and steps, such as coacervation, emulsification, or solvent evaporation. Each method can be optimised based on various factors, including size distribution, yield, stability, drug loading, and encapsulation efficiency.

Here is an example of optimising the synthesis of gelatin nanoparticles via the two-step desolvation method, which is a popular method for making these nanoparticles:

You will need:

a. Dissolve gelatin in a buffer (usually at a concentration of 1-5% w/v).

b. Gradually add the desolvating agent to the gelatin solution under stirring. This process creates the nanoparticles.

c. Once the nanoparticles have formed, cross-link them with glutaraldehyde to make them more stable.

To optimise the process, consider the following variables:

Performing a systematic study that varies these parameters will help you determine the optimal conditions for your desired nanoparticle characteristics. Design of experiments (DoE) can be a helpful statistical technique to optimize this process.

Remember to verify your nanoparticles' size, shape, and surface charge using techniques such as dynamic light scattering (DLS), transmission electron microscopy (TEM), and zeta potential measurements. These techniques can also aid in the optimisation process.

Hope this helps.

Dr Joshua

If you could provide explicit details of the error generated or attach an image of the error message, the community might be able to help you. The information you gave is insufficient

I suggest using dodecylamine hydochloride and the sodium salt of dipicolinic acid. These should be more soluble than the free base and calcium salt, respectively.

To produce Methacrylic Acid is more complicated than to produce Methylmetacrylate. Have You any experience in Organic Chemistry?

[Figure example missing right now.]

Are you looking for something like this?

It isa fixative for histology.

When dealing with bioavailable arsenic (As) in acid soils, it is important to use extraction methods that are suitable for such conditions. Here are two commonly used extraction methods for bioavailable As in acid soils:

1. Mehlich-3 extraction: The Mehlich-3 method is widely used for extracting various nutrients and trace elements from acidic soils. It involves the use of a mixture of strong acids (such as hydrochloric acid and sulfuric acid) at a pH of approximately 2.5. This method is effective for extracting bioavailable As in acid soils and is commonly used in agricultural and environmental research.

2. Modified Morgan extraction: The Modified Morgan method is another commonly used extraction method for assessing bioavailable As in acid soils. It utilizes a mixture of weak acids, including acetic acid and ammonium nitrate, at a pH of approximately 4.8. This method is suitable for acidic pH and has been used extensively for extracting bioavailable As in both agricultural and contaminated soils.

Regarding the specific Soil As extraction method using 0.5M NaHCO3 at pH 8.5, it is not suitable for acidic pH conditions. Sodium bicarbonate (NaHCO3) at pH 8.5 is typically used to extract As in neutral to slightly alkaline soils. The higher pH helps in solubilizing As from solid phases. However, in acidic soils, the use of NaHCO3 at pH 8.5 may not be effective for extracting bioavailable As due to the low pH of the soil.

It is recommended to choose an extraction method that is appropriate for the specific pH conditions of the soil you are working with. The Mehlich-3 or Modified Morgan extraction methods mentioned above would be more suitable for acidic pH soils.

Dear friend Akram Almahmodi

I understand that you are specifically looking for research papers on Nylon 6,10 synthesized from sebacic acid instead of sebacoyl chloride. It can sometimes be challenging to find literature on specific variations or modifications of materials, especially if they are less commonly studied. Here are a few suggestions to help you find relevant information:

1. Expand your search terms: Try using alternative keywords or variations in your search. Instead of searching for "Nylon 6,10," you can try searching for "polyamide 6,10," "PA 6,10," or "polyhexamethylene sebacamide." Additionally, include specific terms related to the synthesis method or starting materials, such as "sebacic acid," "polycondensation," or "polymerization."

2. Broaden your search scope: Instead of limiting your search to academic papers, consider looking for patents, conference proceedings, technical reports, or dissertations. These sources may contain valuable information on specific variations of Nylon 6,10.

3. Explore related literature: Although you may not find papers specifically on Nylon 6,10 synthesized from sebacic acid, you can look for studies on other polyamides or related materials that may provide insights into the synthesis, properties, or characterization techniques applicable to Nylon 6,10. This broader understanding can still be useful in your research.

4. Contact experts in the field: Reach out to researchers or experts in the area of polymer chemistry, specifically those working with polyamides or Nylon materials. They may be able to provide guidance, share unpublished information, or suggest alternative sources for your specific research interest.

5. Collaborate with peers: Engage with fellow researchers, attend conferences, or join online forums related to polymer chemistry. Networking with peers who have similar research interests can help you find relevant literature or exchange knowledge on specific variations of Nylon 6,10.

Remember, research is an iterative process, and sometimes finding specific information can be challenging. It may require a combination of creativity, persistence, and collaboration to address gaps in the literature.

Hi Salim,

Thank you for your answers.

Are the metal salts of organic molecules, carbonate, and ions that are soluble in water do not soluble in HCl?

Besides, are the nitrogen components only soluble in HCl?

I am trying to differentiate organic compounds that are soluble in HCl but not in water, and vice versa.

To adjust the equilibrium pH, you can add a buffering agent to the system. For example, if you need to maintain a pH of 3-4 for the acidic extractant, you can use a buffer such as acetate buffer, which has a pKa of around 4.76. Similarly, if you need to maintain a pH of 9-10 for the basic extractant, you can use a buffer such as carbonate-bicarbonate buffer, which has a pKa of around 10.33.

Here are the general steps to adjust the equilibrium pH using a buffer system:

Choose a buffer system with the desired pH range for your extraction experiment.

Prepare the buffer solution according to the protocol.

Adjust the pH of the buffer to the desired pH range using a pH meter.

Add the buffer solution to your extraction system in the desired concentration.

Mix the extraction system thoroughly to ensure uniform pH throughout the solution.

It's essential to validate the buffer's performance under the specific conditions of your experiment as the buffering capacity of the buffer may be affected by the presence of other components in the extraction system. Therefore, it's recommended to perform a blank control experiment to evaluate the buffer's buffering capacity and the potential interference with the analysis.

thanks

Yes, found its water solubility around 1.5 mg/mL ar room temperature

Phenolphthalein is colorless above pH 10, and pink between 8 and 10. See, attached figure.

Maybe absorbtion instead could be helpful.

Which protease? pI? denaturation state of the substrate? Concentrations and purposed stochiometry? the substrate is reduced or not? Buffer ingredient? Incubation time? Temperature? Any competitive or non-competitive inhibitor? Any activator? PTMs? AA sequence of substrate convenient or not for a particular enzyme ...and so on...

There are many critical aspects for enzyme activity but regarding the pH, you need to state the target enzyme first to verify its optimum activity pH...

The change in pH changes the shape of the enzyme which prevents the attachment of the substrate at the active site and terminates the reaction.

I will show the quoted references:

References

[1]. Nikolaya Velitchkova, Olga Veleva, Serafim Velichkov, and Nonka Daskalova, Possibilities of High Resolution Inductively Coupled Plasma Optical Emission Spectrometry in the Determination of Trace Elements in Environmental Materials, Hindawi Publishing Corporation, Journal of Spectroscopy Volume 2013, Article ID 505871, 12 pages http://dx.doi.org/10.1155/2013/505871

[2]. ISO 10381-2:2002, “Soil quality—sampling—part 2: guidance on sampling techniques,” International Organization for Standardization,

2002.

[3] ISO 11466:1995, “Soil quality—“Extraction of trace elements

soluble in aqua regia”,”International Organization for Standardization,

1995

Microorganisms that grow optimally at a pH less than 5 are acidophiles and sulphur-oxidizing Sulfolobus spp. isolated from sulphur mud fields and hot springs in Yellowstone National Park are extreme acidophiles. Fungi are often dominant members of the soil microflora, especially in acidic environments, and may operate over a wider pH range than many heterotrophic bacteria. Some of the bacterial genera that often perform this activity are Pseudomonas, Bacillus, Rhizobium, Burkholderia, Achromobacter, Agrobacterium, Micrococcus, Aerobacter, Flavobacterium, Mesorhizobium, Azotobacter and Azospirillum. Among the fungi, Aspergillus and Penicillium predominate. However, highly acidic environments are usually inhabited by acidophilic and acidotolerant eukaryotic microorganisms such as algae, amoebas, ciliates, heliozoan and rotifers, not to mention filamentous fungi and yeasts."Extremophiles" are organisms with the ability to thrive in extreme environments such as hydrothermal vents. Since they live in “extreme environments” they can tell us under which range of conditions life is possible.

https://www.aatbio.com/resources/buffer-preparations-and-recipes/citrate-buffer-ph-3-to-6-2,

Acetate buffer can also be useful , but 0.1 difference is very difficult to maintain , for which the pH meter should atleast read pH 3.001 and should maintain the values like pH +/- 3.05 to 2.95 for ph 3.0 , and the pH value varies by temperature as well , so a difference of atleast 3.0, 3.5 , 4.0 can be ideal practical in my perspective

Unfortunately, I could not find these publications with the title and author name you wrote. "Passivation of Nickel Thin Films on Silicon Substrates" by T.S. Sudarshan, et al. unfortunately it didn't come out when I wrote it like this. thanks..

The frequency of naturally transformed plants for dicotyledons has been estimated at 7 % of the studied genomes. In the list of natural GMOs with expressed opine synthase genes, homologues of cucumopine and mikimopine synthase were predominant. (Bogomaz F.D., Matveeva T.V. Expression sequences of opine synthases of natural GMOs based on analysis of their transcriptomes. Biotechnology and Plant Breeding. 2022;5(3):15-24. DOI: 10.30901/2658-6266-2022-3-o2)

Cucumopine was found in tobaco plants by chemical analysis.

If the use is to correct acidity the more important long-term property may be 'lime equivalent' rather than CEC and lime equivalent is readily measured by titration.

The phase transition from bimetallic catalyst to spinel phase can have a significant impact on the textural acidic properties of the catalyst. The textural acidic properties refer to the acidity of the catalyst surface, which is an important factor in determining its catalytic activity.

During the phase transition, the crystal structure of the catalyst changes from a bimetallic structure to a spinel structure. This can result in changes in the coordination and oxidation states of the metal ions, which can affect the acidic properties of the catalyst.

In general, spinel phases tend to have higher acidity compared to bimetallic phases, due to the presence of oxygen vacancies and/or cation vacancies in the crystal structure. These vacancies can create Lewis acid sites, which can interact with adsorbates and promote catalytic reactions.

However, the exact effect of the phase transition on the textural acidic properties of the catalyst will depend on various factors, such as the specific metals involved, the synthesis method, and the calcination temperature. For example, the size and distribution of the metal particles can also influence the textural acidic properties.

In summary, the phase transition from bimetallic catalyst to spinel phase can increase the textural acidic properties of the catalyst, but the magnitude of this effect will depend on the specific details of the system.

Thank you Nitin Fadnavis

But I want to carry out this deprotection in the film state (in-situ).

On sodium phosphate buffer solutions ― You may want to check my post at this related query:

On potassium phosphate buffer solutions ― You may check my post at:

We can predict the pH of mixed Na/K monobasic and dibasic phosphate solutions after the following 'adapted' Henderson–Hasselbalch equation, within the effective buffer range pH = pK_a2 ± 1 (6.2―8.2):

pH = pK_a2 + log₁₀{(C_Na2HPO4 + C_K2HPO4)/(C_NaH2PO4 + C_KH2PO4)}

Here C refers to nominal (formal) concentrations of the salts in the mixed solution. K_a2 is the second dissociation constant of phosphoric acid.

Dear Yifeng Rang ,

Do you know what methylation analysis is and what is its purpose?

No. I was drying it in a Hot air oven.

When you are synthesizing HA, the pH wont increase and versus it will be decreased so do not eorry about it. Besides, the pH can be between 10-11 for HA synthesis

Maybe you may consider to obtain a dispersion (or colloidal solution) of collagen using citrate buffer (pH ~3.4).

Please check answers at the following related discussion, as they may possibly help, particularly if you intended to adjust a pH close to neutral (not specified at the question enunciate): https://www.researchgate.net/post/Can_anyone_suggest_me_the_buffer_conditions_or_methods_for_solubilising_collagen_powder_other_than_acidic_condition

The reaction between malonic acid and phosphorus oxychloride (POCl3) to form malonyl dichloride can be a slow process. To help the reaction take place, you can try the following steps:

If the above steps still do not lead to the formation of malonyl dichloride, it may be necessary to try alternative reaction conditions or to consider using a different reagent for the reaction.

Hello Gabriel Atampugbire

The D-peptides would probably possess little or no immunogenicity is a dogma since they could not be processed and presented to the major histocompatibility complex (MHC) II molecules for recognition by helper T cells or cytotoxic lymphocytes.

You may want to refer to the article attached below for more information on the different roles of D-amino acids in immune phenomena.

Best.

Dear Ellen Kennedy, I think the pH is not the appropriate one. COOH groups should be in their neutral state (lower pH, say less than pH 2). Please have a look at the following paper and the references therin, mainly ref.4. My Regards

10.1016/j.ejpb.2006.11.017

Hi Izzah!

In most cases when preparing solutions you can use as anhydrous compound as a hydrate. But you must calculate the proper weight of the substance, taking into account the difference in the molecular weights of the hydrate and the anhydrous compound.

you can use diluted acetic acid (2%)

Yes. Review the websites of Agilent.com , Waters.com , Phenomenex.com ...

Dear Haji,

thank you for your answer.

However, I checked your mentioned procedure before, but it does not work.

Dear Channarith,

Nice academic approach, good question, maybe connected to the chemical recycling of PA/PET blends! I agree with you that the first idea was to try a common acidic hydrolysis for PA and PET (NB: traditionally it is required high temperature, pressure, enough residence time, etc. /See more information in the literature) e.g. using solutions of sulfuric or phosphorous acid if your equipment (microwave digestion) allows this procedure.

On the other hand, it is important to know if your experimental method is correct. My advice is to try to see if you are able to separately decompose the PA 6,6 or the PET in their monomers/oligomers !

Good luck in your R&D project and best regards,

Marius

PS: You will find a lot of literature linked to the subject depolymerization e.g., this is a Review: Greener routes for recycling of polyethylene terephthalate, https://doi.org/10.1016/j.ejpe.2015.03.001

you can follow reaction progress using HPLC, GC ,IR,NMR...etc

To start with, gelatin hydrolysis is a microbiological test that is used to identify and differentiate between acid-tolerant and alkali-tolerant bacteria. The test is based on the ability of certain bacteria to hydrolyze gelatin at different pH levels.

In general, the pH range for acid gelatin hydrolysis is between 4.5 and 7.5, while the pH range for alkaline gelatin hydrolysis is between 8.5 and 9.5. The test is performed by adding a bacterial culture to a medium containing gelatin and adjusting the pH to the appropriate level. After incubation, the ability of the bacteria to hydrolyze the gelatin is observed by the formation of a gel or a liquid.

It is important to note that not all bacteria are able to hydrolyze gelatin, and the ability to hydrolyze gelatin at a specific pH does not necessarily indicate the optimal growth pH for a particular bacteria species.

@ Linkon, you may try with pressure cooker.

According to the recorded patent

https://patents.google.com/patent/EP2580162A1/en

By means of the method accordant with the invention, gold can be extracted selectively from an acidic aqueous solution or slurry, in which there is a gold- bearing solid, and pure metallic gold can be produced. A suitable diester is preferably used as the extraction reagent in the organic extraction solution, either alone or together with a long-chain alcohol. The extraction solution does not contain any actual hydrocarbon solvent at all. The terms organic phase, organic extraction reagent and organic extraction solution used hereafter all mean the same thing.

In the method accordant with the invention a gold extraction reagent is a diester of 2,2,4-trialkyl-1 ,3-pentanediol and highly suitable is 2,2,4-trimethyl- 1 ,3-pentanediol di-isobutyrate (CAS No. 6846-50-0) described in the molecular structure below. This diester is used generally in the plastics industry, there are several industrial manufacturers and it is reasonable in price. At room termperature the substance is liquid (melting point and boiling point 282 °C). In comparison with DBC for instance, the benefits of the extraction reagent are its low solubility in water (approx. 15 mg/L, 25 °C) and high flash point of 134 °C. Additionally, in research (5) no problems regarding work hygiene or the environment have been reported.

As far as the extraction characteristics of gold are concerned, the oxygen atoms in the molecular structure of the diester of 2,2,4-trialkyl-1 ,3-pentane- diol are essential, but for instance the structure of the carbon chain is not so essential. The invention therefore also relates to molecules in which the side chains of the molecule construction above contain an H atom or some other alkyl group or aryl group instead of one or several methyl groups. When there is later used the word diester in the specification it means the diester of 2,2,4-trialkyl-1 ,3-pentanediol described above.

Gold extraction is based on the fact that the diester (=B) is what is known as a Lewis base, which extracts gold from acidic chloride solution in accordance with the following mechanism:

Borg + (HAuCI4)aq (BH+AuCI4-)org

(B = diester molecule)

so that an ion pair is generated in the organic phase.

It was observed in the tests performed that although the diesters extracted gold extremely well, for phase settling it is advantageous to dilute them with a long-chain alcohol, which is also known to extract gold. However, a diester extracts gold from chloride solution considerably more weakly than the earlier mentioned DBC, and the benefit of this is that stripping can succeed with water.

Besides chloride the aqueous solution may also contain small amounts of bromide or iodide. The extraction stage may take place in one or several steps, but it has been found that even with an extraction stage of only one step good results can be achieved. After the extraction stage, the organic extraction solution is routed to a scrubbing stage, in which it is scrubbed with an acidic aqueous solution in order to remove the metals other than gold and the impurities out of the extraction solution. Other metals in the aqueous solution or slurry containing gold are for instance precious metals other than gold, as well as platinum, copper, iron, antimony, arsenic, selenium, tellurium and bismuth. Some of these are extracted into the organic extraction solution in small amounts as impurities. The gold-depleted aqueous solution or raffinate can be fed for example back to the gold leaching stage (not shown in detail in the diagram). An aqueous solution of hydrochloric acid has proved advantageous as the scrubbing liquid for the extraction solution, since it can be recycled after scrubbing to the gold leaching stages. The concentration of the hydrochloric acid in scrubbing is 1 .5 - 8 mol/L and preferably 2 - 6 mol/L, so that the gold is not scrubbed out along with the impurities. It is advantageous to perform scrubbing in at least two steps. In the first scrubbing step the concentration is preferably greater than 2.0 mol/L. In the second scrubbing step the hydrochloric acid concentration may be the same or different, for instance lower, than in the first step. The hydrochloric acid concentration chosen depends on the quality and quantity of the impurity metals extracted into the organic extraction solution.

The organic extraction solution is routed from the final scrubbing step to the stripping stage. It is advantageous to carry out stripping into pure water, whereupon the tetrachloro complex of the gold is broken up. It is preferable to perform stripping in several steps, either as countercurrent or crosscurrent extraction. In the crosscurrent extraction accordant with Figure 1 a separate scrubbing liquid is routed into each scrubbing step, which in this case is pure water fed into both steps. In this case crosscurrent extraction is preferred because chloride is also scrubbed out of the organic phase in stripping. It is advantageous for gold stripping that the chloride concentration of the water is as low as possible in each step. The aqueous solutions from the steps of the stripping stage are combined and routed to the reduction stage. Reduction is carried out for instance with oxalic acid or sodium oxalate or a mixture of the two. The reduction reactions are as follows and as a result a pure pulverous gold product is obtained:

2 HAuCU + 3 (C02H)2 2 Au + 6 C02 + 8 HCI

2 HAuCU + 3 (C02Na)2 -> 2 Au + 6 C02 + 6 NaCI + 2 HCI

Gold can also be reduced from aqueous solution by means of electrolysis. The carbon dioxide generated in the oxalate reduction of gold may be absorbed by a suitable scrubbing solution using known methods. The amount of carbon dioxide is proportional to the amount of gold generated i.e. it is completely marginal and does not affect the process or its economic viability.

However, it is clear that, in the same way as extracting gold from a gold- bearing solution, gold ore, concentrate or some other gold-bearing solid such as anode slime, ash, scrap or the ion exchange material, activated carbon or adsorbent used in gold recovery can be treated with the method accordant with the invention or solvent-in-leach (SIL) method, where extraction is performed directly from the solids-bearing hydrochloric acid solution, i.e. from the slurry without a separate leaching stage.

The gold-bearing solution or slurry, such as for example an anode slime, may also contain selenium and sometimes also tellurium and antimony. In tests in which there was not only gold in the feed exiting acid leaching but also selenium, it was observed surprisingly that the diester also extracts selenium. The observation differs from the behaviour of selenium in connection with DBC for instance, in that selenium is known to stay in the extraction raffinate i.e. in the post-extraction aqueous solution . A process chart is presented in Figure 2, according to which the selenium and any tellurium and antimony extracted into the organic extraction solution can be recovered. According to the chart, selenium is extracted once again into the diester reagent and stripped into the aqueous phase. The precipitation of selenium can be done by known methods, for instance by reduction with sulphur dioxide in accordance with reference .

Caro acid is the peroxymonosulfuric acid and is one of the strongest oxidants known (E0 = +2.51 V). It's unstable and decomposes to the hydroxyl and HSO4(.) radicals due to a relatively weak O-O bond.

You may want to see my post on the pH of a sodium lactate (NaC₃H₅O₃) / lactic acid (C₃H₆O₃) aq. sol. elsewhere at this forum:

About pH or titration of mixed acid solutions at RG:

About the titration of a mixed phosphoric acid / sulfuric acid aq. solution with sodium hydroxide aq. solution; cf. my posts at:

About the pH for sodium acetate / acetic acid solutions with added hydrochloric acid; cf. my posts at:

About the pH of mixed lactic acid /sodium lactate and acetic acid / sodium acetate solutions or buffers ― also with strong monoprotic acid added; cf. my posts at:

About the pH of mixed H₂SO₄―HNO₃ aq. solutions:

https://www.researchgate.net/post/Do-you-know-a-method-for-titration-of-HNO₃-H₂SO₄-mixtures

On the pH of mixed H₂SO₄―HCl and H₂SO₄―HCl―HI aq. sol.:

About mixed citric acid / sodium citrate with nitrous acid / sodium nitrite solutions or buffers:

https://www.researchgate.net/post/How-do-I-calculate-the-mass-of-citric-acid-to-add-to-a-NaNO₂-solution-to-reach-a-certain-pH

Two main causes:

(1) System was loaded with sample dissolved in an incompatible liquid (injection solution must match mobile phase !);

(2) Your injection port or rotary valve seal may be damaged (probably from clogging/fouling with sample, overloading, precipitation etc). Inject pure mobile phase and see if the problem still occurs of if pressures are normal.

If pressure is abnormal then: Perform routine service on the AutoInjector, inspecting and cleaning the stator, needle seat and capillaries and replacing the normal wear parts. Be sure to only use the injector with chemically compatible solvents too (we see a lot if new users running solvents that the injector is NOT compatible with, resulting in damage). Once the valve has been repaired, then flush the flow path down in both the main and by-pass positions and verify correction pressures while isocratic conditions exist (constant flow, constant composition and temperature).

Thank you for your response Sir Vikram U Pandit

May I ask why do you say that solvothermal synthesis is the best technique for TiO2?

Dear Jürgen Weippert, thanks very much for your insightful response.

Common laboratory borosilicate glassware  ̶  often either called 'borosilicate 3.3' or Pyrex® glass ─ is expected to be seriously corroded by concentrated (conc.) aqueous solutions of phosphoric acid above ~120 °C. Use of conc. H₃PO₄ (> 30 wt%) from ~40 ºC to ~120 ºC is also not recommended, in general, but can be found acceptable after carefully consideration of the particular experimental circumstances involved by experienced users. Below ~40 ºC, corrosion is expected to be small, but prolonged contact of the glassware with conc. H3PO4 should be also avoided, particularly when volumetric glassware is used or when contamination of the contained liquid with ions contributed by glass corrosion must be avoided to any appreciable extent. Besides these generic guidelines, it would be also advisable to refer to the technical literature that may be found issued by the glassware supplier.

About pH or titration of mixed acid solutions at RG:

About the titration of a mixed phosphoric acid / sulfuric acid aq. solution with sodium hydroxide aq. solution; cf. my posts at:

About the pH for sodium acetate / acetic acid solutions with added hydrochloric acid; cf. my posts at:

About the pH of mixed lactic acid /sodium lactate and acetic acid / sodium acetate solutions or buffers ― also with strong monoprotic acid added; cf. my posts at:

About the pH of mixed H2SO₄―HNO₃ aq. solutions:

On the pH of mixed H₂SO₄―HCl―HI / aq. sol.:

Feedstock (oil) acid values determine the catalysts to be used.

I agree with Peter Donkor :)

It has to do with difficulties in estimating carotenoid content of food. Certain assumptions are made about the efficiency of their conversion to retinol in humans.

National Institute of Health, USA guidelines:

IU retinol = 0.3 mcg RAE

RAE can only be directly converted into IUs if the sources of vitamin A are known. For example, the RDA of 900 mcg RAE for adolescent and adult men is equivalent to 3,000 IU if the food or supplement source is preformed vitamin A (retinol) or if the supplement source is beta-carotene. This RDA is also equivalent to 18,000 IU beta-carotene from food or to 36,000 IU alpha-carotene or beta-cryptoxanthin from food. Therefore, a mixed diet containing 900 mcg RAE provides between 3,000 and 36,000 IU vitamin A, depending on the foods consumed.