We value your privacy
Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds.
I was seeing some uses of ionic exchange to recover NH4 by ionic exchange with other cations in a specific matrix. And it brought me to question what drives an ionic exchange to be better towards an ion in solution and not so good to another?
I thought maybe the charge of the cation would influence but maybe is not so relevant as here
K and Ca are ahead of Na and Mg. Maybe the hydration radius as an important role in it instead? And can pH of the solution where ionic exchange is done affect also the selectivity of the ionic exchange knowing it can affect the lattice charge of the matrix?
Is there a way we can estimate this? or just by trial?
Does anyone know of, or use, commercially produced surfaces for contact measurements (control material)? As an example, is there a producer of PTFE discs with highly controlled surface roughness and chemistry that I can purchase? I have not found any....
"The perovskite solution for the solvent quenching method (MAPI) recipe was prepared by dissolving 553.2 mg PbI2 and and 181.23 mg MAI in 1 ml anhydrous DMF/DMSO (4:1, v:v) to obtain a 1:0.95 molar ratio solution (PbI2:MAI) with a concentration of 42.96 wt %."
How can one get 553.2 mg of PbI2 and 181.23 of MAI (CH3NH3I) to be dissolved in 1 ml solution to obtain a 1:0.95 molar ration solution when the molar mass for PbI2 and MAI are 461.01 g/mol and 158.97 g/mol respectively.
Dear Mike A. James, the molar masses of the two components you provided are correct, but the details in the procedure are also correct. The authors do not use 1 mmol of PbI2 but they use 1.2 mmol of PbI2 (553 mg) and 1.14 mmol of MAPI (181 mg), i.e. the two starting materials are employed in a molar ratio of 1:0.95.
I have synthesized and crystallized a compound but after the XRD study i found out that the crystal structure of this compound already exists (the attached file A is my structure B is that of literature)
but i noticed some differences :
- My structure's volume is large by around 7.6 A
- some minor difference in cell parameters.
- Clear difference in R1 (mine is better).
- Difference in number of asymmetric units Z'.
My questions are:
- Is my structure considered as a new structure ?
- Can i publish it ?
i have another structure (3rd one ) of the same compound but with a solvent inside the cell
- Can i publish both structures (A and the 3rd structure ) in same article as new polymorphs ?
ps: attached files: projection along the C axis of both structures with parameters
Thank you in advance
From this picture I cannot state with certainty if it is the same structure (= the same molecule with the same crystal packing) or not, because the representation is different. The coordinates of the atoms are chosen differently with respect to the origin in A and B. You can probably shift your atoms in the unit cell so that the two structures look more similar.
From the unit cell it seems the same structure: the difference in volume is "negligible" and the different reported Z, Z' is likely due to a different definition of the moiety formula or sum formula.
But, in principle, the unit cell is not enough to decide if it's the same structure. As suggested, you can compare the simulated powder patterns. I also suggest to carefully compare the crystal packing by analyzing the intermolecular contacts and examining a bigger packing range (like for example 2x2x2 unit cells). Some programs also allow to overlay two crystal structures, to visually compare them.
In any case, you can most probably publish your structure along with the solvated form, with more focus on this latter, as it is new. Compare if there are real differences with the literature structure, for example, were they measured at the same temperature? Any conformational differences? I suggest you adopt the same atom labelling names and the most similar setting to the published structure, in order to facilitate the comparison both for you and for the readers.
In the age of Covid19, is there a basic conflict between science and superstition in the discipline of medical knowledge? Are there some simple, sensible, robust and reasonable ways to distinguish a scientific statement (or fact) from a superstitious statement?
To stay focused, the topic will concentrate on science versus superstition in the scientific discipline of medicine. We will try our very best to stay focused and not stray off track. it is very easy to wander off message and be all over the map. i will try to summarize the key conclusions from time to time.
In the age of the Corona Virus, there are so many statements out there. The statements may not be scientific. But if they are not scientific, are they false? Are they fake? Are they simply statements based on superstition.
What should we do if people believe in statements that are not based on science? Should we be polite and tolerate their beliefs?
As long as people do not harm others, then from society’s point of view, the fact that people hold non-scientific hypotheses is probably benign. However, the trouble starts when the same people act these beliefs, and then cause harm to others. The question arises: what should society do in this case?
Based on the discussion, there are two assumptions and four categories.
Assumption1: Beliefs cannot be justified or unjustified.
Assumption2: hypotheses can be disproven
Scientific hypotheses that are based on justified facts in natural causation. Or scientific hypotheses have not been disproven (I prefer the negative formulation because we may never be able to prove anything but we are unable to disprove it.)
Since science cannot give a definitive answer, there are many competing answers that merit our attention, and we may not be able to select among them.
Non-scientific hypotheses are unjustified facts that may be “proven” in the future with better evidence and facts.
Pseudo-scientific hypotheses: not sure where these fit in?
Superstitions are unjustified beliefs in supernatural causation.
Joseph Tham, thanks for a thought provoking question. I think we should tolerate and respect beliefs and ideas that are not considered scientific. Our intolerance of such beliefs and ideas could be the result of a lack of understanding of the science behind them. We should therefore subject them to rigorous testing using the scientific method. A practical example is the fact that the World Health Organization has not dismissed out of hand the herbal remedy from Madagascar that is claimed to prevent illness from COVID-19. Instead the remedy is going to be tested using established scientific principles. The null hypothesis can then be rejected or accepted. This is how Indigenous Knowledge Systems contribute to scientific advancement.
chemistry is one of an interesting science in the world. but in most developing country student is nit prefer to learn chemistry. i mention the most two cases: in developing country mostly no laboratory accumulation, and there is no reference materials and so on.
Dear Bram Kuijer, in such redox reactions, it is not possible that all reagents are being reduced. Oxidation and reduction must always take place simultaneously. In this case., the metallic copper is oxidized by iron(III) chloride, i.e. FeCl3 is the oxidizing agent which is itself being reduced to Fe2+. On the other hand, you start with metallic copper (Cu0), which is the reducing agent. During the reaction, Cu0 is oxidized to Cu2+, i.e. the copper foil slowly dissolves.
I keep receiving e-mails from a "Dr. A Lesnevskyi M.D." from a so-called Internal Medicine Review journal. The journal has now several issues dating back March 2016. I checked the doi (digital object identifier) of some articles and most of them are not registered in Crossref. However, I was really surprised that a couple of articles were in Crossref. It is written in the website that they are indexed in Pubmed (National Library of Medicine (PubMed) ID: 101691967), but I was not able to find a single article there. Their ISSN numbers are fake, I was not able to find them in the ISSN portal (https://portal.issn.org/). A two story building at 712 H St NE Washington DC 20002 is the location of Gold Spot, a payday loan and check cashing business. The website uses the same fake address.
A little piece of advice if you are thinking in sending a polite reply that you are not interested: It is not a good idea to reply to any predatory publisher, even if it is to decline their offer or ask them to stop emailing you. They can then sell your email contact as a verified address to other publishers. Always block or mark as junk.
I wonder if all these "papers" published there are actual studies or fabricated texts only to embellish the website and attract more researchers willing to pay for a publication, with fees ranging from US$ 799 to US$ 2,999. For me this is clearly a predatory, fraudulent, fake journal.
I can confirm the insistence of this (as well as a lot of others, to be honest) "journal"... the not so clear scientific quality of the editorial proposal can argued just looking at the following email:
Dear Dr. Luca Di Persio,
I am hoping to contact the corresponding author of "Mild solutions to the dynamic programming equation for stochastic optimal control problems"
Would that be you? I was wondering if you are still working in this field as it aligns well with one of the theme issues I am planning for this year. Perhaps you could tell me more about your work in this area.
Could you please get in touch with me so we may discuss this?
%%%%%%name cancelled %%%%
Medical Research Archives(MRAJ)
... being the type of the cited paper far from possible" medical researches" 🤔
Any thoughts and recommendations on good articles, textbooks and resources on the topic of permanent magnet materials (e.g. neodymium) in terms of phenomena associated with their ageing and degradation under temperature, chemical, mechanical and electrical/electromagnetic stressing.
Several studies on combustion of bio diesel/petroleum fuel blends in IC engines and other power generation / combustion devices discussed extensively about the influence of fuel unsaturation on NOx emissions. A fundamental question arises on how we quantify fuel unsaturation?
I would like to start a discussion on the topic - How to quantify fuel unsaturation ? what would be an appropriate index to quantify unsaturation irrespective of the family of origin of fuels - like methyl esters, ether, alcohol , alkanes, alkenes, alkynes or aromatics or a weighted combination of aforementioned categories.
Our research group's take on this -
We have established a parameter - Degree of unsaturation that serves as a common platform across different fuel families (esters/alkanes/aromatics) to quantify the effects of fuel unsaturation, particularly with petroleum/bio-diesel blends. DOU can be evaluated based on the average molecular formula of the fuel alone without involving complex and expensive experimental procedures such as those involved in the measurement of iodine number and bromine number.
If interested, please follow the link to access the research work we have conducted at our laboratory to investigate the effect of fuel unsaturation on nitric oxide emissions.
Firstly, there are many reports which conclude that IV is a measure of total unsaturation but not degree/extent of unsaturation. This is one reason why IV is not used to quantify the Oxidative Stability of a biodiesel, which is a function of unsaturation. Similar to what you have done, researchers have long back disregarded IV to measure DU. In fact, DU proposed by Ramos et al. does not take into account the effect of polyunsaturated esters. Consequently, Wang et al. (J Fuel Chem Technol, 40 (4) (2012), pp. 397-404) and Shashank et al. (10.1021/acs.energyfuels.6b01343) have modified it and designated it as DUm long back, which I believe would be of some help to you.
Secondly, NOx emission is a function of fuel property, cetane number (CN) and in-cylinder conditions. Having said that, let me make it clear that CN of a neat ester increases with its chain length and decreases with the DU. But many researchers have reported that the behavior would not be the same in case of mixture of esters viz. a biodiesel. It is actually the balance between CL and DUm which affects CN, that influences NOx emissions. So, I would suggest you to relate both CL and DUm to NOx emissions rather than DU alone.
The relationship between rates of lipid oxidation and moisture is complex. The amount of water, the water activity and the state of water in a food, along with other factors, must all be considered.
For most fresh or tissue foods that have moisture contents between 60 - 95% have a water activity very close to 1.T he mode of deterioration at this water activity is generally microbial or enzymatic in nature. Direct lipid oxidation (i.e. not enzyme-mediated) is not an important source of deterioration at this high water activity since other modes of degradation will deteriorate the food first.
Concentration, freezing, and drying are mechanisms by which the water activity of food can be reduced. Such processes may bring the food into the intermediate moisture or low-moisture region where direct lipid oxidation becomes a more important mode of degradation. Also, during dehydration, free radicals can be formed which accelerates lipid oxidation. Freezing can also lead to the acceleration of lipid oxidation rates through the concentration of substrates and catalysts in the unfrozen portion of the system.
On the other hand, Chou et al. (1973) found that water activity primarily affects matrix swelling and thus substrate/reaction site availability as well as catalyst mobility.
Hereinbelow the tow common theories related to the relationship between water activity/content and lipid oxidation are briefly discussed:
Unlike most aqueous chemical reactions, the rate of lipid oxidation that takes place in the oil phase is observed to increase as water activity is decreased below the monolayer (i.e. water molecules that are bound tightly to the food surface). This can be explained by considering the role of water in this reaction. It has been suggested that the monolayer of water—or rather, the water saturation of polar groups in lipids—is necessary to cover the surface of the lipid, preventing it from direct exposure to air. This monolayer is essentially “bound” water with limited mobility and is assumed to not participate in chemical reactions. Several studies have found that a variety of foods are most stable to lipid oxidation at a relative humidity or aw consistent with the monolayer.
On the other hand, water can form a hydration sphere around metal catalysts such as Cu, Fe, Co, and Cd. In the dry state, the metal catalysts are most active. As water activity increases, the metals may hydrate which may reduce their catalytic action thus slowing the rate of lipid oxidation.
This monolayer theory, however, cannot be applied universally.
Glass transition theory
According to the glass transition theory, one important function of water is its ability to act as a plasticizing agent. The plasticization of a matrix involves swelling of the polymer matrix when moisture is increased. The resulting increase in free volume might allow for faster diffusion of substrates in the aqueous phase which may lead to faster reaction rates. Plasticization may also increase the contact of the absorbed aqueous phase with the lipid phase. The number of catalytic sites increases such that the rate of lipid oxidation increases.
The above discussion shows that water plays both protective and prooxidative roles in lipid oxidation. In some foods at low aw near the monolayer moisture content, water is protective, presumably because it provides a barrier between the lipid and oxygen.
While the classic food stability map proposed by Labuza et al. (1972) shows lipid oxidation having a U-shaped relationship to aw, no U-shape was also observed; lipid oxidation actually slowed as aw increased as the case of freeze-dried food.
Overall, monolayer and glass transition concepts might not effectively predict lipid oxidation reactions in some foods if oxidation is primarily occurring in the lipid phase and thus would not be significantly impacted by water and the physical state of proteins and carbohydrates. On the other hand, water can play a major role in lipid oxidation chemistry if reactions are primarily promoted by water-soluble prooxidants such as metals. Unfortunately, the causes of lipid oxidation in low-moisture foods are poorly understood, which could be why measurements of water activity, monolayers, and glass transitions do not consistently predict lipid oxidation kinetics.
Treatments such as pyrolysis, hydrothermal carbonization, hydrothermal liquefaction, hydrothermal gasification are being used to process algae and yield products such as lipids, lipid-rich hydrochar, biocrude, methane and hydrogen. These treatments also produce biochars as a product of thermal decomposition of organic material under limited supply of oxygen at temperatures less than 700oC. Biochars have potential for use as a soil amendment, both to improve soil quality and to sequester carbon.
The SARS-CoV-2 genome was rapidly sequenced by Chinese researchers. It is an RNA molecule of about 30,000 bases containing 15 genes, including the S gene which codes for a protein located on the surface of the viral envelope (for comparison, our genome is in the form of a double helix of DNA about 3 billion bases in size and contains about 30,000 genes).
Comparative genomic analyses have shown that SARS-CoV-2 belongs to the group of Betacoronavirusesand that it is very close to SARS-CoV, responsible for an epidemic of acute pneumonia which appeared in November 2002 in the Chinese province of Guangdong and then spread to 29 countries in 2003.
A total of 8,098 cases were recorded, including 774 deaths. It is known that bats of the genus Rhinolophus (potentially several cave species) were the reservoir of this virus and that a small carnivore, the palm civet (Paguma larvata), may have served as an intermediate host between bats and the first human cases.
Since then, many Betacoronaviruses have been discovered, mainly in bats, but also in humans. For example, RaTG13, isolated from a bat of the species Rhinolophus affinis collected in China's Yunan Province, has recently been described as very similar to SARS-CoV-2, with genome sequences identical to 96 percent.
These results indicate that bats, and in particular species of the genus Rhinolophus, constitute the reservoir of the SARS-CoV and SARS-CoV-2 viruses.
Here is an excerpt from an online CleanLink statement I replied on another, similar link in response to RG member Christian G Meyer's correction of my mistaken assumption that SARS-Covid-2 is "equivalent" to COVID-19:
"According to the U.S. Centers for Disease Control and Prevention (CDC), there are actually multiple types of coronaviruses, some of which commonly cause mild upper-respiratory tract illnesses. There are seven types of coronavirus that infect humans, three of which evolved from animal strains.
Because there are many coronavirus types, referring to it simply as "coronavirus" is very general. The CDC and World Health Organization (WHO) encourage experts to use COVID-19 when referring to this new disease, a novel (or new) coronavirus that has not previously been seen in humans. In COVID-19, ‘CO’ stands for ‘corona,’ ‘VI’ for ‘virus,’ ‘D’ for disease and 19 indicates the year it was discovered.
Just as the general public has become familiar with this terminology, officials have also begun using SARS-CoV-2 in connection with the recent outbreak. Severe acute respiratory syndrome coronavirus 2, shortened to SARS-CoV-2, is actually the virus that causes COVID-19 (the disease). As the name indicates, this virus is genetically related to the SARS-associated coronavirus (SARS-CoV) that caused an outbreak of severe acute respiratory syndrome (SARS) in 2002-2003, however it is not the same virus.
How do all these terms fit together? "Coronavirus" is a generic term that includes a large family of viruses, similar to saying someone has the flu. SARS-CoV-2 is a specific virus that can cause COVID-19, a disease. As WHO explains, this is similar to differentiating HIV and AIDS — HIV is a virus that causes AIDS. Outlined on their website, "People often know the name of a disease, such as measles, but not the name of the virus that causes it (rubeola). . . .
. . . . Whether talking about the virus or the disease, it is important to practice and share best practices for cleaning and disinfecting."
Seems like a silly question but I'm having trouble with searching for CIF files via https://www.ccdc.cam.ac.uk. I've used it before but I was on university campus so I think I was able to use more than just the simple search function. I think I used structure search before and I was able to type in the compound name and the structural formula to get a CIF file, but now as I'm working from home, I don't have a CCDC licence and so I'm restricted to just the simple search. I've tried just typing in the compound name and no results come up. Will I need to search compound names with a paper that potentially has a CIF referenced? Or have I just misremembered how to use CCDC! Any and all help appreciated, thanks!
So I have conducted an experiment looking at the size of silica nanoparticles. However, the results I obtained showed that at a lower mass concentration of SiO2, the volume and radius of individual particles are greater than that of higher SiO2 mass concentration.
I can't seem to find an explanation regarding this and was thinking that at lower mass concentration the individual particles colliding somehow caused them to agglomerate together causing the bigger particle size.
It seems to come from the same group of people: E. Padron, Ph.D., Dr. L. Smith, M.D., P. Jimenez, Ph.D., A. Siozos, M.D., A. Lesnevskyi, M.D., A. Nikitakis, MSc, Ph.D., A. Umana, M.D. These people were approaching me before in the name of the journal "Internal Medicine Review".
I see some very good answers - we do the estimation by measuring the change in thermal conductivity of the space. The measurement can be more meaningful if you know the composition of the mineral deposit. The thermal conductivity of common water system scales is known. If the accumulation is, in fact, deposited, not grown in place - then the thermal conductivity model would be more relevant within repeated accumulation/settling of solids in that location.
Thermal conductivity is an accurate means of measuring the relative thickness but the results are more material with repeated measures or an accurate knowledge of the physical and chemical composition of the matter of interest.
You have answered your own question. Proper chromatography methods require detection methods which are applicable to the samples under analysis. You may want to review the types of instruments, detectors, columns and materials available at your school before deciding on a final approach. Have someone in the school's analytical instrument lab assist you.
For HPLC samples with weak or no chromaphore, you will need to use a detector that does not rely on wavelength based light absorbance such as an RID, ELSD, CAD or MS, to name a few. Put a little time into researching this basic question so you will better understand the uses and limitations of these methods and detectors. I often suggest my students start with a keyword search on the web (GOOGLE or BING) to find examples and articles to review. This is one of the best ways to learn. Once you have familiarized yourself with the basics, be sure to ask your teacher for help in setting up and running some example methods.
BTW: You may also be able to derivatize some of your samples and use GC/FID or GC/MSD as an alternative to HPLC (only if the samples are appropriate).
I read that after leaching of oxidized zinc concentrates with sulfuric acid, the resulting solution is purified from harmful impurities like iron, copper, cobalt, nickel. And with a weakly acidic medium, pH = 5.2–5.3 iron ions are practically precipitated by the formation of hydroxides.
If a person is good in mathematics and has command over it, that means he has good logic aptitude and grasping ability. If now he want to do research in Fluid mechanics of course he can. He should start with reading the basic physics books and gradually increase the level to engineering fluid mechanics. Which, at this stage, should be a matter of not more than 6 focused months. after that he will be able to do like masters. Do not run behind paper publication from the start it will a by product of your focused learning and problem solving.
I am PhD in analytical chemistry and I make part of a multidisciplinary team working on the development of a web based solution focusing mainly on treatment and management of environmental chemistry data. But in order be more acertive in this project I need to interview researchers worldwide to trace a more realistic picture on how they deal with their environmental data.
Could any of you please help me by giving me a 40 minute interview? We could make it via WhatsApp or Hangouts (or other choice).
Hydazine hydrate solution in water is basic (pH=11) but the solution of Hydrazinesulfate in water is acidic (pH = 3). So to get the hydrazine hydrate from hydrazine sulfate , the pH of the hydrazine sulfate solution has to be tuned to pH= 11.
Here the procedure:
Dissolve the Hydrazinesulfate in water ( 1 g in 30 ml), check the pH (then add Ambersep 900 hydroxide from resin (or any other OH from resins) and adjust its pH to 11. Filter the solution to obtain Hydrazine hydrate.
I have used this procedure recently, it works very well.
I want built a small biochemistry lab for research purpose ( Phytochemical Study).
It refers to the extraction, screening and identification of the medicinally active substances found in plants. Some of the bioactive substances that can be derived from plants are flavonoids, alkaloids, carotenoids, tannin, antioxidants and phenolic compounds.
Please give me some guideline and references for built a small laboratory.
Mar 9, 2020
I don't think that anyone will be able to give a satisfying answer, since nobody knows what exactly you want to do and which infrastructure your university can offer:
There are multiple extraction methods, but you can probably use relatively simple instruments. Depending on your extraction procedure, you might need a rotavapor or just remove the solvent with a flow of inert gas. Once you have an extract (or fractions), you want to screen it for some biological activities. You might want to check for antibacterial activity, which is relatively easy. You might want to check for the effect on different mammalian cell cultures (cell culture lab and microscopy required) or you might want to test for some activities on animal models.
Of course, it makes a huge difference if you can use an autoclave at the institute, some cell culture lab from a different group, maybe a mass spec facility or if you have to set everything up on your own.
Furthermore, think of groups or services that could help you. For example, you will not set up a cell culture lab, if you want to check for cytotoxic effects of some substances - you could rather have a collaboration partner or company do it for you.
I think you should really narrow down what you want to do and which instruments would be absolutely required for this. Check, which instruments you could use at your institute, which things could be done by collaboration partners and which instruments you would have to purchase. Then, you could think about "nice to have"-equipment...
It looks like neither the journal nor EndNote provide a style file, thus you will have to edit an existing style (perhaps ACS). If you have EndNote on your computer (not the plug-in but the stand alone program), go to Edit/Output Style/Edit "ACS"/Bibliography/Templates. Edit the journal article template, then save the edited style with a new name. When you reopen Word, you should see it when you "Select another style".
Hello! I am working with short-single walled carbon nanotubes dispersed in water. There is .3g in 30ml of water. I need concentrations of 10ug/ml, 20ug/ml, 30ug/ml, and 40ug/ml.
I was told that since the CNTs are already dispersed that we basically need to take X amount of our stock solution and dilute it with X volume of water and we will have our desired concentrations.
I am a horticulture major and this is my first venture into a project of this magnitude. I can't seem to find a chemist or bio professor to help me, can anybody help me out? Would really appreciate it.
Ethyl Benzoate protonates with HCl to form protonated Ethyl Benzoate and Cl- (Screenshot Attached). After the Ethyl Benzoate is protonated with HCl(non aqueous) in a non aqueous solution, would the protonated Ethyl Benzoate then serve as a cation, and the solution's PH can then be measured by a standard electrode?
Would the H ion pop back off of the oxygen in the presence of an electrode? Essentially I am looking for a way to measure the PH (or relative PH) of this non aqueous solution.
I hope you feel well today. I will write what I understand from your equation. In really adsorption presence is separation method or transfer containment from liquid or gas phase to the solid phase. Therefore, there are products waste as solid can control it for disposal or reuse. All treatment processes need an energy source for work but adsorption does not want that. The low cost of operation and the initial cost of adsorption is the advantage. On the other hand, we use the adsorption process for removal of the low initial concentration of the heavy metal that can't be removed from water by precipitation. Today, the researcher tries to find now mater that has high adsorption capacity at the same time made this material from waste ( the name of adsorbent is super-adsorbent ) such as metal-organic network , nanoparticle, polymer, and hydrogel.
Alginate is an anionic polymer and on the other hand Rhodamine B is a cationic dye. Theoretically these two should be boned by ionic bond. Does it happen? More suggestions and experience are greatly appreciated. Advanced thanks!!
You may not want to use the following advice if you are weighing hazardous substances: don't wear gloves. They are a big source of static. Check with the lab head whether this is permissible if you want to try it. Wash your hands afterwards.
Otherwise, minimize static by avoiding a lot of motion of the solid in its container. In other words, avoid shaking or tapping the container. Use metal spatulas, not plastic ones. If you are not weighing the solid directly into the final container, use glassine weighing paper rather than a weighing boat. Use the smallest feasible piece of weighing paper, not necessarily a whole one.
The HC gas upstream T,P is known and downstream P is know. A cooling effect is likely to occur since moving from a high pressure to low pressure across the control valve. One of the things I am not sure how to estimate is the Joule-Thomson coefficient.
I think that B is the correct answer. Usually Mixing solvents with statement 1:1 means equivolume mixing of components, (1+1=2volumes diluted finally x2) which finally yields halved concentrations of constituents. This should be premixed if used as Hplc mobile phase and degased, and pumped through special pH basic resistant column matrix.
Yes, if electron withdrawing groups are prsent in near or conjugation to phosphrus, then n then only chance for more labile oxidation. but any phosphites are highly undergoes to oxidation so inert atmosphere is needed.
A plasma bonded PDMS device to glass slide when treated with pluronic, will make the surface hydrophobic? I know that pluronic is used to avoid deposition on surfaces, but what does it really do to make the surfaces deposition free.
I would like to start a project for the construction of rockets as a project for high school students. Starting with the development of a solid fuel (KNO3 + sugar) which is the safest method for the production? What additives can I use? I have seen from very simple elaborations, to more elaborate methods with the same components. Heat the mixture and manipulate it how dangerous it is? How do I estimate efficiency?
I have experience with r-candy propellants, and its not very dangerous as other solid propellants (for example APCP). If you apply the basic safety procedures you will be very safe (lab coats, safety googles, masks etc). If you make the propellant by heating method, then you must be carefull with the burners, because when you put the propellant in the mold through casting method, its very important to ensure that the propellant will not fall on the burner by mistake. Because you have to make the propellant with students, I will recommend to you to mix well the KNO3 with sugar as raw materials and do not use the heating method.
Also, you have to consider that these propellants are not easy to ignite them, so be sure that you will ignite the propellant from far, using ignition wires, not with lighter.
If you want to increase the burning rate, you can decrease the KNO3 particle size or you can add a small quantity of Fe2O3 red iron oxide as catalyst. But if you do that, you have to keep in mind that it will be more dangerous.
It is very good to learn to your students the significance of safety.
in a previous question relating to this topic here in ResearchGate, Dr. @Angel Cuesta, gave the following, very clear, explanation.
The Tafel slope simply tells you how much you have to increase the overpotential to increase the reaction rate by a factor ten. This will be determined by the magnitude of the change in the activation energy for a given increase in overpotential (when you change your potential 1 V, the Gibbs energy of the process will change by 1 eV per electron transferred, but the activation energy will only change by a fraction of this, and this fraction determines the Tafel slope). In a reaction involving only one step with one electron transfer, the Tafel slope will be determined by the symmetry factor, which is usually 0.5 (corresponding to a Tafel slope of 120 mV). In a more complex reaction involving several steps and several electron transfers, the Tafel slope will be determined by the rate-determining step and by the number and nature (i.e., involving an electron transfer or not) of the preceding steps. So, essentially, from the Tafel slope you can deduce whether your rate-determining step involves an electron transfer or not, as well as the number of electrochemical (involving an electron transfer) and chemical (not involving an electron transfer) steps that precede it. If you propose a reaction mechanism, you can calculate what the corresponding Tafel slope should be and, if it does not coincide with the experimental one, the mechanism cannot be correct.
For more details, you can have also a look at the following notes:
I have performed a demethylation reaction using BBr3 and neutralized it with sodium bicarbonate solution and removed the water by lyophilization. Now, I want to separate my product from reaction mixture. My product is soluble in methanol and water. Could anybody help me to give idea for separation of the product?
SiF4 gas will appear and take in consideration that SiF4 is toxic and corrosive. In moist air it fumes, whereby it is easily hydrolyzed to give H2SiF6 and SiO2. However, in my opinion the most toxic / hazardous substance in this system is certainly HF. Utmost care must be exercised when working with HF, especially if it is a concentrated solution (40%) or even anhydrous. It easily penetrates the skin and can lead to serious injuries
I have to do few toxicity tests in which silver is involved. To do that i have to prepare a stock solution using silver nitrate (AgNO3) salt. The concentration of exposure in the tests is referred to silver itself, not to the compound. I need to know how much silver nitrate salt i need to have the concentration of 5 g/L of Ag. I would be really glad if someone could also explain/show the mathematical and logical reasoning behind the answer.
I am removing carbonates from clay and sand samples. So, I treat the sediments with H2O2. I need to wash the sediments to remove acid residues. I am thinking of heating the sediments with ultra-pure water over hot plate and subsequent evaporation. The process can be repeated for 3-4 times over hot plate. Will it work and act as an alternative method of centrifuge washing?
Ashok - H2O2 is used to remove organic matter from sediments - not carbonates. If you are trying to remove carbonates, but wish to leave any clay minerals unaffected, you should use a buffered sodium acetate/acetic acid solution (pH 5.3). If you aren't concerned about the clay minerals, dilute HCl would be fine. E-mail me if you would like the method.
Saida, If you have a look at a Dieke diagram it'll be apparent to you that the energy states of La are well separated (gs and es) way above its bandgap so no emission line will fall in the visible region. And La doesn't have 4f electrons as the other lanthanide ions do. Also, other emissive lanthanide ions which are often used as emitters, have energy levels that are separated by energies falling in the visible range. However, due to the inner shell configuration of these 4f ions, it's very unlikely that you can directly excite a 4f-4f transition in these- so you'll see little-to-no emission intensity. However, if you have La in the material it can absorb the incident energy and efficiently transfer it to the emitting lanthanide ion in an indirect way. But this energy transfer is strong enough that it populates the emissive states of your lanthanide activator and you'll see the fluorescence occurring from them. That's why you see an increase in luminescence efficiency in the presence of La.
as i want to find out the impact of ceramide on my cells in DMEM-F12 medium. I dissolved C16-CER in Ethanol and added it to my medium. After having a look through the microscope, i see that it precipitates.
). Therefore, I think it is increasing solubility and subsequently effectivity of the compound. For the preparation of a C2-CER BSA mixture you can follow the instructions by ENZO. It worked well for me.
Actually, when we try for the annealing of potassium niobate, we suffer from those cracks on the tube. The niobium gets reacted with Si and forms Niobium Silicate. Those cracks are at inner surface of the tube. And cracks get propagated and unfortunately that tube get damaged.
I am currently proposing a study about the formation of free PUFAs (EPA and DHA) in raw oysters treated with acidic sauces. Based on a study by Sajiki et al. (1994), free PUFA formation may be caused by the activation of lipolytic enzyme in the oysters treated with acetic acid. However, I am confused regarding this mechanism since the oysters are not alive. Can this explanation be used for dead oysters? Is there a better explanation for the formation of free PUFAs?
Dear Gabris Mahamid,
Such a database aggregated and sorted at this stage is being developed. It has not been tested and therefore cannot be seen. The development is of large companies such as: Web of Science, Scopus, Google Scholar and Google Academia, Microsoft Academic, Semantic Scholar and others.
There is only a partial finding at this stage of these data companies on specific topics in specific areas.
Wishing you success in research.
Dear all, some journal use the experimental details in a separate file with a specific DOI. It is named 'Supplement file'. It is mentionned in the first page mother file. Generally it is free downloadable. My Regards
I will soon start a new project in which electrochemistry is applied in organic chemistry. It will be totally new for me and for the group where I work. Do you have some tricks or advise for this topic?
The electrosynthesis provides a better environment for the generation of reactive species by dissociation or bond forming processes. The reactive carbon species are used in various synthetic transformations, essentially C-C bond formations. Oxidation and reduction of functional groups are also important reactions in organic synthesis. A major advantage of electrosynthesis is the reduced formation of side products.
A magazine is definitely not the same as a Journal. Magazines normally carry popular articles, not original work. A Scientific Journal publishes original scientific work not published elsewhere. 'Letters' or 'Notes' are of shorter length. It may include a comment on an already published recent paper by the author or someone else. Normally, Editor takes decisions on 'Letters' and 'Notes'. Seldom are they are sent to reviewers.They get published quickly. A full length paper in a reputed Journal has to undergo peer review process and may take up to an year or so to get published.
A resazurin-based assay was produced with ampicillin against E.coli , negative control was just LB media and E.coli and the positive being ampicillin and E.coli, with resazurin for the readings. Plate readings were taken initially and then every 30 minutes for 2 hours. The only data I have is the plate readings and the initial concentration of ampicillin added. How would I work out the final concentration of ampicillin?
I want to mix Graphdiyne into NDP-V that is non-fullerene polymer and seldom used as electron transport layer. could you please predict its chemical properties or kindly send some research articles of someone already did it.
There have been a lot of initiatives to include active learning exercises in both lecture and lab. Many have observed good results in information retention and elimination of misconceptions. I have observed some of these results firsthand, and active learning is something I think is quite valuable. Here are a few resources, but there's lots of info out there:
For curriculum, I have noticed a shift towards an "atoms first" approach, but I haven't seen anything conclusive on its effectiveness. My feeling is that it works well for some students, not for others (just like any approach). I have yet to see any good methods on stoichiometry excepting certain teachers who have a knack for explaining it well.
This article suggests focusing on training teachers and developing innovating learning material:
The lightest elements (mainly hydrogen and helium and in trace amounts lithium and beryllium) were formed about 100 seconds after Big Bang through the Big Bang nucleosynthesis (this process lasted up to 20 minutes after Big Bang).
After the formation of stars new elements, from helium to iron, are produced in stellar nucleosynthesis (thermonuclear fusion: CNO cycle,proton–proton chain reaction and triple-alpha process) during stellar evolution.
Elements higher than iron are produced in supernovae through the r-process and s-process.
A very good book about this and generally about properties of stellar interiors and the structure and evolution of stars is: "The Physics of Stars" A. C. Phillips.
About the nuclear physics of stars, you can see also a book of Christian Iliadis "Nuclear Physics of Stars".
I am using 1g/L stock solution of Copper and Zinc prepared from Copper Sulphate pentahydrate and Zinc Chloride, respectively. I am using the stock solution to prepare standard solutions of concentrations between 0.1 mg/L to 10 mg/L by dilution. I am preparing the standard solutions everyday by dilution from the stock solution to calibrate the Atomic Absorption Spectrophotometer.
My question is that is it OK if I store the standard solutions, which are of quite low concentration and use them for future use instead of preparing everyday from the stock solution? If yes, what is the maximum storage period for which I can use them?
Store the stocks in the fridge, i.e. cool and dark, and they should last for months. What tends to happen is that they slowly concentrate due to evaporation. So use good containers. The more dilute solutions are more stable in acid. Even 1 mg/L is quite concentrated beside the solutions used to calibrate ICP-MS so it should be OK for a few days. Beyond that rely on testing for yourself.
Yesterday on December 5th, 2019 at 3:45 p. m. a full bottle of our homemade brandy on the small kitchen table on our kitchen spontaneously exploded. I am a retired university professor in chemistry and very knowledgeable in physics but I do not understand how could it happen?
I have been looking into MSDS of KOH of 0.1 M, and it says use proper ventilation area while working. But in my lab, we don't have fume hood to work with. And I am not able to find any safety sheet on 0.001 M KOH solution. I would also like to know about any possible health effects of this.
I need to find a proper method to prepare sample solution by digestion for Pt-Pd-Rh elements from spent automotive catalysts. Any suggestion except application of microwave-assisted digestion would help me.
I want to synthesis the CuInSexS2-x QDs and as I am elementary in chemistry, I want to know that how to determine the sub x in such structure in practice (mean in the synthesis of CuInSexS2-x QDs in Lab) ? and could you introduce me a source for more study about this fundamental issue in chemistry?
You can measure the stoichiometry of a sample using X-ray photoelectron spectroscopy, although XPS is normally very surface sensitive so there may be some difference between the measured st. and the bulk of the QD depending how small it is.
Do there exist any compounds, fluorophores, dyes, quantum dots, phosphors etc that can emit or fluoresce non-linearly without needing ultra-high intensity illumination (such as pulsed femtosecond laser)? That is, with a UV led for example and with this non-linear emission being dominant?
Prof. A. Tikhonov already nicely summarised the most important issues concerning up-conversion. As far as phosphors are concerned, there are a couple of materials that can show rather efficient NIR to VIS up-conversion at moderate irradiation levels. These are: NaGdF4:Er,Yb; Gd2O2S:Er,Yb; BaY2F8:Er,Yb and YOCl:ErYb.
All of these materials make us of the mechanism of Sensitised Energy Transfer Up-conversion (S-ETU), while Yb3+ is the sensitiser and Er3+ the green or red emitter. Important is that the host material has solely low phonon energies, otherwise the process is easily quenched by electron-phonon coupling. Good luck!
Hi all, working on a task where HF acid gas may be present due to Li-ion battery combustion (faulty batteries, over-changing, transport/vibration) in a container. Curious how one would design a filter or neutralize this gas in order to lessen damage to humans and surroundings? I imagine this may be a chemical engineering question, which I have no experience with. Thank you!
When we want to trap hydrogen fluoride on a filter in order to estimate its concentration in the atmosphere we use filters soaked with sodium carbonate. I think you could try to adapt this method to your issue. You can see an exmple of the use of this method here:
I'm dissolving PCL in TFE for electrospinning purposes, and the paper I'm following has detailed how to do a 10% w solution by dissolving 0.4 g PCL in 4 mL TFE, but this doesn't seem right to me based on previous training I've received on how to calculate a w% solution which required me to dissolve 0.763 g PCL in 5 mL TFE. I'm feeling like the latter method is really a w/v%, but it always produced good results, so for future purposes which calculation should I go with?
Christian Chavis Christian Chavis In pharmacy, a w% or more commonly w/w% is the number of parts by weight of the solute (or active ingredient) contained in a hundred parts by weight of the final preparation. so to get a 10% W/W solution you have to dissolve 0.5 gm of your solute (PCL) in 4.5 gm of the solvent (TFE, you can convert this to volume of TFE by dividing 4.5 by the density of TFE). I hope this is of use. Best wishes.
I am conducting experimental simulations to study the PM 2.5 concentration.I have tried several chemistry options ranging from RADM2 MADE/SORGAM to MOZCART aerosol chemistry. The simulation was successful but I am getting very low values of PM 2.5 of the order of 0.1 to 0.9 ugm-3 which should be of the order 100 to 900 ugm-3. I am confused as to where I am making mistake. has anyone come across similar kind of issue with PM 2.5 concentration?. what should be my next step in resolving this issue?.
I am using EDGAR HTAP and FINN data as an input data to include PM2.5 estimates. I am having doubts especially in the above emission input files. kindly check and see if there is any changes needed in the namelist flie of emission data especially the spc_map part of the namelist.
I have seen reasonable amount of PM2.5 over India from the WRF-Chem using the RADM2 MADE SORGAM. As you mention that changing chemistry to MOZCART also did not improve the model performance in your case, it is possible that your input emission has some issue. Pl check wrfchemi files how PM emission data is written there. If unresolved, you may send me a sample plot of PM2.5 emission and I can tell if these values look fine (and also correct units). All the best.
Hello RG fellows, I am trying to coat/deposit a thin layer via PECVD on Polypropylene substrate. The functionality of the coating will be water-vapor barrier. Which precursors are the best for this purpose? Thanks!
it is not easy to reply because of many options and variables.
By my knowledge, if the thickness is higer than some 0.2-0.3 mm and the substrate is not greatly flexible, then 100 - 500 nm thick SiOx based coatings obtained starting for example from HMDSO are a good solution. I tried in the past with multialyer coatings based on different SiOx design with satisfactory results in terms of barrier properties. Otherwise, if the substrate is greatly flexible the film risks to be fractured and lose its barrier properties. In such case polymeric coatings with lower barrier properties but higher flexibility should be more effective. Best regards, Simone
I'm creating an analytical tool for aromatic molecules that uses geometry optimization and connectivity data from Gaussian 6, but I'm having trouble with the connectivity output. When computing optimization with connectivity for Benzene using hf/3-21g, I receive the connectivity output:
whereas I'm expecting an output like this:
1 2 1.5 6 1.5 7 1.0
2 3 1.5 8 1.0
3 4 1.5 9 1.0
4 5 1.5 10 1.0
5 6 1.5 11 1.0
6 12 1.0
Does anyone have any recommendations about what basis set I should use or what I'm getting wrong?
'G09 does not print connectivity data in the out file. However, if you check your output file, you can find 'Distance Matrix'. Once you have done optimization, visualize the output and if you save gif file then you can get the connectivity data.
I’m trying to make a 4:1 ratio of two solutions. One solution is a 5mL soln. at 20% (w/v) and the other is a 100mL soln at 10% (w/v), respectively. Normally this is easy when both concentrations are the same, but how do I do the ratio with different concentrations? A mentor is recommending diluting the 20% solution to 10%, but this would defeat the purpose right? I’m sure there is a mathematical formula that would make things easier to understand. Thanks all.
I am trying to prepare CuN(CN)2 (=Cu[dca] = Copper(I) dicyanamide) by reducing an aqueous Cu(II) solution to Cu(I) with K2[S2O5] then adding stoichiometric amounts of Na[dca]. However upon addition of the reducing agent I form an orange/brown precipitate in a green solution, I believe this is as a result of the disproportionation of newly formed Cu(I) to Cu (orange/brown precipitate) and Cu(II).
The overall reaction for the reduction is as follows:
Cu2+ + 2HSO3-+ 2H2O --> Cu+ + 2HSO4- + 4H+
And the disproportionation:
2Cu+(aq) --> Cu(s) + Cu2+
Are there any other reducing agents which may work better or any ways to stabilise the Cu(I) formed in solution to prevent the disproportionation and allow further reaction with Na[dca]?
Are you sure that your precipitate is Cu metal rather than Cu2O, which is also reddish in colour?
You could try ascorbic acid as reducing agent - I've used it to make CuCl (very easy method, much nicer than any other I've tried!). To get rid of excess ascorbic acid with less risk of oxidation than if you use water, use methanol: ascorbic acid is significantly soluble in methanol, much less soluble in ethanol.
I added V2O5 as precursor for vanadium 0.5g in 30ml of DI water. I added 0.5g of oxalic acid anhydrous in 10ml of DI water, which functions as a reducing agent. I added the reducing adent to the precursor solution, thereby my total volume now is 40ml containg V2O5 and oxalic acid. I stirred the solution for half an hour at 60C, but the solution only turned to green solution instead of blue solution according to the references. Can anyone explain it? I added oxalic acid anhydrous instead of oxalic acid dihydrate, could this be a reason?
Joel Kumlin The display is incorrect, the temperature was maintained at 60C using a thermometer. Thank for your feedback on mentioning that stirring rate also affects particle size, could you suggest me a suitable RPM which I am advised to maintain? (i was maintaining here 700 RPM)
Stable isotopes are defined as non-radioactive forms of atoms and they exist naturally in the nature. I would like scholars to suggest me some literature or any other aid where I can understand how isotopes are formed, in terms of energy levels and how can we create them artificially in the lab environment. Also, how are these stable isotopes more advantageous when compared to conventional element.
Hello! There is a lot of resources available in the net regarding stable isotopes. I was able to download an old copy of Robert Michener's and Kate Lajtha's book (2nd.ed, 2007 Blackwell Publishing) on Stable Isotopes in Ecology and Environmental Science. It is quite informative and easy to understand.
It might interest you to know that stable isotopes are naturally occurring. So far, I have not encountered a study (maybe my search is limited) making use of stable isotopes for application other than as indicator for certain parameters. Regarding your question on whether these isotopes are more advantageous than conventional elements, it might really depend on what you want it used for.
ORCID provide a persistent digital identifier (an ORCID iD) that distinguishes scientict from other researchers and a record that supports automatic links among all your professional activities. The same functionality is in RG and even more, and the identifier is a link to RG.
I am working on several novel fuel cell types catalyzed by organic-anorganic composite catalysts and I am grateful that I was given a A4 sized piece of membrane made from quaternized Poly(styrene). I have been working on crosslinked PVA membranes but those really aren’t favorable since they don’t really have a high tensile strength and their consistency is rather highly flexible and rubber-ish.
Since I fear that the membrane will be used up in far future I will need an alternative for further work on my alkaline-anion fuel cells, now that I cannot use pva and since getting PVP for a PVA-PVP membrane is very hard here in Germany I need another idea for a making a stiff membrane.
Just dissolving regular PS, dissolving it and adding some Triethylamine as quaternizing agent probably won‘t work, will it? So are there possible alternatives to polymer membranes?
To the best of my knowledge there are three companies with materials potentially suitable to alkaline AEMFCs.
1. FuMa-Tech was mentioned above - FAA-3 was an early standard in AEM fuel cells and I used it extensively. To the best of my knowledge it is QA-based but not styrenic backbone chemistry, and from first-hand experience the membranes are quite tough. I can't find the FC-grade in the store, but it's in the spec below; ionomer solution should be available in NMP even if I can't find it listed on the site either.
2. Dioxide Materials has materials available but I have much less first-hand experience and don't know the suitablility in fuel cell applications. They appear to have styrenic backbone chemistry and need to be treated right but they may be suitable to your needs. There is ionomer but the disclaimer is that it is designed for CO2 electrolysis so again I'm not sure about the compatibility.
3. With full disclosure I'm a co-founder and part of the company, Ionomr has alkaline-stable AEMs with a set designed for AEMFCs and ionomer compatible with low-boiling solvents for consistent electrodes.
i'm working on counter electrodes for DSSC. VO2 shows good thermochromic property. Are there other transitional metal oxides which show the same effect? What is the physics behind this significant property of VO2?
Lacorre and Torrance published a lot on this topic in 90s-00s.
The reason, in case of perovskite material, is due to the bandgap overlapping of the 2p O orbitals and 3d metal orbitals by changing the temperature. In ABO3 perovskite, you have BO6 octahedra (metal atom surrounded by oxygen octahedra cage). The angle B-O-B between two octahedra is responsible of the bandgap energy.
The transition has been described as the ZSA model (Zaanen, Allen, Sawatzky):
At low temperature, there is no overlapping, insulator behavior
At high temperature, lattice distortion and bandgap narrowing, that can go up to the overlapping of 2p O and 3d metal orbital: metallic behavior.
The angle between the B-O-B is directly dependent of the RE size (it is 180° for cubic and decrease as the RE size decrease).