# Tag Info

## Hot answers tagged absorption

12

To expand on Thawn's answer to #1 a bit: In quantum systems, a particle is bound to discrete states when it is constrained by a sufficiently deep potential well; otherwise its energy is continuous$^\dagger$. So, the existence of solvated electrons (alt., electrides) implies that the potential field established in certain solvents in certain situations ...

12

Both of your questions could benefit from more background, so please forgive me if I understood something wrong. However, I'll try to answer as best I can: The excess electron in liquid ammonia is not really independent, otherwise, as you stated correctly, the electron would not absorb a certain wavelength but act as a black radiator/absorber like in a ...

8

The reason why PEG is suitable for this purpose has many reasons including the wood chemistry and degradation of wood in water. Degraded wood usually very characteristic chemical losses. The cellulose of the wood is usually lost due to bacterial action and/or due to the action of the water itself. Over long period of time wood looses water-soluble ...

8

One fallacy in your question is assuming that the particles 1) are spherical and 2) only accessible on the outside. The press release linked says that this material is nanoporous - the particles are perforated by pores "all having a diameter smaller than 10 nano meters". The extra surface area is inside these pores. Spheres have the lowest surface-area-to-...

7

Yes it is very common particularly in the more rigid type of molecule. The best example is chlorophyll and this overlap of absorption and emission leads to energy transfer in photosynthesis. The reason for the overlap is that the excited state potential energy profile is very similar in shape but slightly shifted (as displacement) to that of the ground ...

6

At hydrous equilibrium will the "stronger" desiccant contain virtually all of the water? Or is the equilibrium distribution of water a function of the desiccants' relative "hygroscopy," rates of sorption, or some other factor(s)? "Rates" aren't relevant for questions about equilibrium. I am trying to imagine a series of tests in which two different ...

6

No it doesn’t. Measurements can in principle be made at any wavelength. If there are two colored specimens in the same solution, it is actually better to measure at the wavelength where the difference between the spectra is as high as possible. Measuring at a peak has some advantages: the absorbance is high, giving a good signal/noise ratio, and if the ...

4

Yes. The ones I have are known commercially as Jelly Marbles or Orbeez. They're sold at gardening stores, home decor, and online. They're used as toys but also as gardening products that absorb excess moisture in wet conditions and supply water in dry conditions. Mine grow up to about 1.5cm from a starting diameter of ~0.1cm. I've been told that some grow up ...

4

According to Transportation Information Service: Salt: At up to 74% relative humidity and 20°C, salt does not absorb any appreciable quantities of water vapor. The critical water content of sodium chloride (NaCl) is 0.5% at 74% relative humidity, which is the flow moisture point at which salt begins readily to absorb water vapor, and increases such that, ...

4

In Advanced Drug Delivery Reviews, 2001, 46, 3-26, (DOI) Lipinski and coworkers write: Too many hydrogen bond acceptor groups also hinder permeability across a membrane bi-layer. The sum of $\ce{N}$s and $\ce{O}$s is a rough measure of H bond accepting ability. So, for the empirical rule of five it's simply the number, nothing more. In the cited article,...

4

With the experimental setup you describe, you would not observe any intentional polarization dependence, because the light passes only through a beam splitter, not a polarizer. There can be unintentional polarization due to the nature of optical materials and manufacturing, caused by the diffraction grating, the polarization contribution of mirror ...

4

Yes, it is meaningful, but often ignored for practical reasons. In the lab, e.g. in a desiccator, you would just use a large excess of the desiccant of choice which would always work. It’s often more meaningful to classify them as to whether they are acidic, basic or neutral. But let’s assume we wanted to create that scale. For simplicity reasons, let’s ...

4

Mirror image spectra are only observed in solution and then only if the ground and excited state potential energies have almost exactly the same shape. Thus in rigid molecules such as anthracene a good mirror image is observed but not in more flexible molecules such as stilbene ($\phi-C=C-\phi$). The spectra of each vibrational level is wide in solution due ...

3

The skin is able to prevent some things from passing in and out of a person but it is not a perfect barrier. The lipophilic things like nicotine, hydrogen flouride, VX, hexane and iodine vapour can pass through undamaged skin. These things are able to dissolve in the fatty parts of skin. Then they diffuse in through the skin into the person. Thus they enter ...

3

Ions are hygroscopic because they form very stable, low energy hydrates, which are thermodynamically favorable over water vapor. I.E. salt attracts water vapor because the hydrated salt is lower energy than the water vapor. Other very porous materials are hygrosopic due to capillary action. Water vapor is attracted to the surface initially due to a variety ...

3

Read closer: Most of the hygroscopic substances are drying agents not all drying agents are hygroscopic substances. First Terminology: Hygroscopic: Absorbs water from air Drying agent: Removes water from organic substance Your book did not exclude other materials from being considered drying agents. It just said many of the substances that are ...

3

The intensity transmitted at wavelength $a$ where the extinction coefficient is $\epsilon_a$ is $I_a=I_{0a}\exp(-\epsilon_a L C)$ with path length $L$ and concentration $C$, and similarly for a second wavelength $b$. If, for clarity, we let $x=\epsilon l C$ then then $I_a=I_{0a}\exp(-x_a)$ and $I_b=I_{0a}\exp(-x_b)$. The total transmitted light is $I_t=I_a+... 3 Yes, it does, and especially for calibration curves [1, p. 439, 455]: For spectrophotometric analysis, we normally choose the wavelength of maximum absorbance for two reasons: (1) The sensitivity of the analysis is greatest at maximum absorbance; that is, we get the maximum response for a given concentration of analyte. Sensitivity$b$is the slope of your ... 3 If you are looking for something that can be made using elemental oxygen as an oxidizer and reversibly release the excess oxygen below 1000 °C, sodium peroxide beats potassium peroxide by using lighter metal atoms. It can be prepared by reacting sodium with oxygen in two stages (forming sodium oxide in the intermediate stage) at 130–200 °C and releases the ... 3 From the Jablonski diagram, The mirror image is only true if you are talking about transitions from$S_0$to$S_1$(absorption) and$S_1$to$S_0$. Also read about Kasha's rule. Quinine is the most famous fluorescent molecule, its$complete$absorption spectrum is not a mirror image of its emission spectrum. 3 Negative absorbance in a double beam instrument has no physical meaning because absorbance, by definition, cannot be negative. It ranges from$0$to$\infty$. Instrumentally, all that means is that somehow the sample cuvet is transmitting more light than the reference cuvet. In other words, the measured absorbance of the sample is less than than measured ... 2 There are materials that absorb methane under ambient conditions. A quick Google Scholar search for "metal organic framework methane" shows some of the most recent and popular synthesized materials that can do this. Dr. Shengqian Ma at University of South Florida is a big figure in the field, and he currently collaborates with my computational research group.... 2 The silica gel granules are granular silicon dioxide (SiO2), the same matrial from what is the normal sand. The pure SiO2 has the same effect to health as when you eat sand. But because the granules are larger, may cause appendix problems (im not an doc). Anyway, this is not chemical related problem. It can cause dehydratation or other problems, what is ... 2 The answer varies with the type of food and the type of condiment. Both are very complicated mixtures, so a same combination of food and condiment can display varying levels of adsorption/absorption depending on the region/compound being analyzed, but in general, I expect that while all of chemical/physical adsorption and chemical/physical absorption happen ... 2 This site explains the use of oil on wood fairly well: Oil is made of molecules small enough to seep down into the wood rather than merely sit on top. As a result, oil makes wood look richer and more translucent without adding a film on the surface. There are two different types of oils that woodworkers use: drying and non-drying oils. Drying oils will ... 2 Let us assume that baking soda works by not simply absorbing, but reacting with acidic/odiferous substances via an acid-base reaction. So, for example if you had rancid butter in the fridge and it gave off the nasty-smelling butyric acid, that acid would react with the baking soda to give sodium butyrate plus carbonic acid (which breaks down to carbon ... 2 Some salts have high tendency to be hydrated, like Li salts. The reason is that their hydration energy is very high, meaning that when they are hydrated, lot of energy is released. Since lower energy is always more stable, such salts tend to show high hygroscopy. 2 I don't believe it is strictly necessary to determine the subgroup induced by a vibration in order to determine if a vibronic transition is allowed. You can simply use the equation from your 2nd quoted block of text. For example, consider whether an electronic transition would be allowed between a$b_1$and$b_2\$ state of water. Without including ...

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