20

(I'm no chemist, but here's my take on it) Let's see: I’m an alcoholic, and I really hate having to dole out large amounts of cash to purchase your usual "drinking"-ethanol. So I get this amazing idea to separate the ethanol by distillation (methanol has a lower boiling point than methanol, so what I'll really be doing is distilling out the methanol, ...


17

When a compound is "pure" it means the contents of that compound are exactly what we claim them to be. If something is $99\%$ pure, that means $99\%$ of it is the expected material (in this case, meth), and 1% is other non-meth compounds. Purity matters in chemistry and biology because the other compounds can be very nasty. In theory, if you had a bag of ...


14

Assuming you mean NaCl - the common "salt" (chemists call lots of things salt!). If you extract the salt by physical means, it's a physics question. Assuming that the "dirt" is not (or poorly) soluble in water, I would simply dissolve the salt in water, filter the liquid, then recrystallize (by evaporation of the liquid) and weigh the resulting crystals. ...


13

OK, so after a bit of researching this is what I've found. First of all,why does the dust not settle in the water in the first place? Well, dust forms a kind of a suspension. The particles are all similar and ionized, so therefore they have a similar charge (positive, I think) causing them repel each other and stay separate. And because they're so small,...


13

Yes, this is possible and is a process called reverse osmosis. It is based on a membrane which lets water pass but not the salt ions (and other water contaminants). From Wikipedia: The membranes used for reverse osmosis have a dense layer in the polymer matrix -- either the skin of an asymmetric membrane or an interfacially polymerized layer within a thin-...


12

So-called food-grade stuff is meant to be consumed by humans. It's important that every single compound of a foodstuff is food-grade or at least GRAS. In the European Union the law giver has defined the state when a compound is good for consumption as "save". Lab-grade chemicals often contain toxic materials, so when something is called lab-grade it is not ...


12

The procedure you are describing sounds like fractional freezing. Acetic acid is frequently purified by this method, hence 100% acetic acid is often called "glacial" acetic acid. As an example of how this works, let's consider a mixture of acetic acid and water. Acetic acid has a freezing point of 16.6 oC. Water has a freezing point of 0 o. They form a ...


12

Reason is salt dissolve very easily with water, forming very strong bond. Not only salt there are also other minerals. To break this bond we need technology as well as energy and both of them are very expensive(today). There are two methods by which we can break this bond: Thermal distillation: Thermal distillation involves heat: Boiling water turns it ...


11

One use of a liquid nitrogen cold trap is to collect organic and water vapors that are removed from a system under vacuum. In this case, the vapors are collected as ices (solids). See this reference which has some useful information on Schlenk line safety and use. Where you want to be cautious is when your collection is finished. You do not want to keep ...


11

A pure compound is one that does not have anything else accompanying it — and thus is something entirely unreachable if your detection system is good enough unless you’re going for supercooled $\ce{^3He}$. However, typically lab grade chemicals are sold in purities of ${99+}~\%$ and extra special care is taken so that the remaining impurities do not affect ...


11

Thorium dioxide can be dissolved in the mixture of hydrofluoric acid and hydrochloric acid, as described by Kluger and Lieser in 1981.1 Proceed with caution since hot condensed acid are known to be highly corrosive and hydrofluoric acid is also highly toxic and penetrating. Kluge, E.; Lieser, K. H. Dissolution of ThO2 in HCl/HF-mixtures. Radiochim. Acta ...


10

The reason criminals don't undenture alcohol is probably because it's cheap and easy to make your own alcohol at home. Plus it's legal in the US (click on G1) and most other English-speaking countries. You can get equipment kits from anywhere between 50 and 200 USD (more expensive kits will get you tools that make things easier or improve quality and add ...


10

In Soviet Russia, where alcoholism was widespread and homebrewing illegal, undenaturing alcohol was a pretty common thing - a part of national culture, in a way - along with such practices as: drinking straight down various non-food grade products containing ethanol or extracting ethanol from them or stealing ethanol from industrial processes or, well, ...


9

Put them into a pot with some club soda and a piece of aluminium foil and pour over a hot water. I am familiar with this process. I am not familiar with the other. Perhaps someone else can provide an answer for it. What happens chemically during these procedure - why does it work, and what are the byproducts of these reactions? This process cleans ...


9

Generally laboratory grade reagents have not been prepared with human consumption as a consideration, but with regard to their use as a chemical reagent. For example, $95\%$ ethanol is mostly ethanol and $5\%$ water. This is fine for cleaning equipment, or using as a solvent for a TLC. If you want to use ethanol as a reagent, however, you want to use ...


9

As iron is one of few metals not forming amalgams, Almost all metals can form amalgams with mercury, the notable exceptions being iron, platinum, tungsten, and tantalum. ..it should preferably contaminate the mercury surface. I would try, perhaps repeated, dropping mercury, e.g via punched filtration paper to sulphuric acid bath. It can be combined ...


8

According to Decomposition of Sodium Tetraphenylborate, which relates to the Savanna River site for nuclear weapons material production, Stable aqueous NaTPB solutions are a transparent, flesh-toned color. During the initial stages of decomposition (or instability),the solution turns a golden color. As the quantity of TPB- that has decomposed ...


7

HCl is a gas at room temperature and diethyl ether is a low boiler. Both will have significant vapor pressures and, therefore, exist in the vapor phase above your solution. The HCl and diethyl ether in solution will continuously maintain an equilibrium with the vapor phase. As you bubble nitrogen through the system it will continuously sweep the vapor out,...


7

The refluxing of methanol or ethanol over magnesium is indeed the method of choice to dry these solvents. As far as the iodine is concerned, this is a classical trick, which is also used to initiate Grignard rections. Is is assumed that magnesium iodide is formed, which is soluble in the alkanols. As a result, a fresh, activated metal surface is left ...


7

There nothing special about boiling that is doing anything. For example, you can put a beaker of water under vacuum and get the water to boil at room temperature, but that won't kill any bacteria or render any viruses impotent. It's purely a heat thing. You want to destroy any pathogens that may cause illness. Sufficient heat will denature proteins in a ...


7

First, from Boundless.com (Chemical Composition of Urine), "Urine is an aqueous solution of greater than 95% water, with the remaining constituents, in order of decreasing concentration urea 9.3 g/L, chloride 1.87 g/L, sodium 1.17 g/L, potassium 0.750 g/L, creatinine 0.670 g/L and other dissolved ions, inorganic and organic compounds (proteins, hormones, ...


6

Is it possible to obtain pure, precipitated iron with no oxidation by some chemical process? Very pure iron can be obtained by pyrolysis of iron pentacarbonyl. Iron metal obtained in this manner is in fact called carbonyl iron and is commercially available. $$\ce{Fe(CO)5 -> Fe(s) + 5 CO}$$ Doing this yourself is very dangerous, however, because iron ...


6

Well, scientists usually purchase the purest grade of chemical available if they want to use it for a reaction. (Leading to the absurd case that the less pure reagent grade is often dismissed for the purer analytical grade.) Usually, special care is taken for these chemicals to remove especially those impurities which could hurt most — you really don’t want ...


6

In case your mercury didn't come with an assay of the supplier, or has been used before, you might want to remove oxidizable metals by repeatedly dripping the mercury though diluted nitric acid and distilled water. Subsequent distillation of mercury is certainly possible (at 25 mm Hg or lower), and has been reported by E. H. Riesenfeld and W. Haase in Ber. ...


6

Armarego's Purification of Laboratory Chemicals suggests using dichlormethane–hexane pair instead of ethanol–water; it also lists crystallization from warm ethyl acetate, ethanol or petroleum ether as alternative [1, p. 342]. Dibenzalacetone [DBA, bda, trans-trans-1,5-diphenyl-1,4-dien-3-one, 1,5-(bisphenyl)-penta-1E,4E-diene-3-one] [538-58-9] $\ce{...


6

Ethyl acetate is the solvent of choice in Org. Synth. 1932 article. The procedure was submitted and checked. The following is the the full procedure stated in Organic Syntheses.; Collective Volume (Ref.1): A cooled solution of 100 g. of sodium hydroxide in 1 l. of water and 800 cc. of alcohol (Note 1) is placed in a 2-l. wide-mouthed glass jar which is ...


5

If you look at the (average) composition of seawater:         you will find that NaCl is the main solute of this complex solution. Its concentration is 10 times higher than that of the next constituents (magnesium and sulfate). So, it seems to me like a simple NaCl solution is a good approximation for your experiments. Regarding testing salinity of water, ...


5

You seem to have the right idea. To elaborate, take the specific example of the positive azeotrope of (roughly) 96% ethanol and 4% water. If you begin with a mixture containing less than 96% ethanol, distillation will result in a distillate more abundant in ethanol and nearer to the azeotropic composition. That implies the residue will necessarily be ...


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