What is a vacuum

The word vacuum in the English language is the same as the Latin word meaning a completely empty space. In practice, the word vacuum is used to describe any space in which the pressure is less than atmospheric pressure. Further, in order to specify the quality of a vacuum, various adjectives are used. Table 1.1. lists a selection of these terms, the associated pressure range, and the number of molecules per cubic centimetre that such a vacuum contains. It is clear that even the best known vacuum, in outer space, is not absolute. A knowledge of the amount of gas in a reaction volume at the operating pressure allows an assessment to be made of its possible effect on the reaction taking place. 

Pressure p/Torr Number of molecules/cm at 273 K Quality of vacuum 

Once a high vacuum system has actually been used for chemistry , i.e. has contained compounds other than the constituents of air, it is very difficult and tedious to evacuate it to below 10 Torr. 

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What is a vacuum Simply stated, a vacuum is the absence of pressure—the absence of gaseous particles. Very high vacuums are stated as very low pressures, on the order of 10 6 mmHg. 

Both PVD and CVD belong to vacuum technology. So what is a vacuum ... 

The question arises concerning what is a reasonable reference level. This problem becomes clear by means of another thought experiment . Let us assume that an electron from the vacuum level far outside the electrolyte is captured by a redox ion ML+i)(iiq) (oxidized species) in the electrolyte, which leads to the formation of M (liq) (reduced species). We have then the reaction... 

A membrane divides a rigid, well-insulated 2-m tank into two equal parts. The left side contains an ideal gas [cp = 30 J/(mol K)] at 10 bar and 300 K. The right side contains nothing it is a vacuum. A small hole forms in the membrane, gas slowly leaks out from the left side, and eventually the temperature in the tank equalizes. What is the final temperature What is the final pressure ... 

The course of a surface reaction can in principle be followed directly with the use of various surface spectroscopic techniques plus equipment allowing the rapid transfer of the surface from reaction to high-vacuum conditions see Campbell [232]. More often, however, the experimental observables are the changes with time of the concentrations of reactants and products in the gas phase. The rate law in terms of surface concentrations might be called the true rate law and the one analogous to that for a homogeneous system. What is observed, however, is an apparent rate law giving the dependence of the rate on the various gas pressures. The true and the apparent rate laws can be related if one assumes that adsorption equilibrium is rapid compared to the surface reaction. 

The angles ot, p, and x relate to the orientation of the dipole nionient vectors. The geonieti y of interaction between two bonds is given in Fig. 4-16, where r is the distance between the centers of the bonds. It is noteworthy that only the bond moments need be read in for the calculation because all geometr ic features (angles, etc.) can be calculated from the atomic coordinates. A default value of 1.0 for dielectric constant of the medium would normally be expected for calculating str uctures of isolated molecules in a vacuum, but the actual default value has been increased 1.5 to account for some intramolecular dipole moment interaction. A dielectric constant other than the default value can be entered for calculations in which the presence of solvent molecules is assumed, but it is not a simple matter to know what the effective dipole moment of the solvent molecules actually is in the immediate vicinity of the solute molecule. It is probably wrong to assume that the effective dipole moment is the same as it is in the bulk pure solvent. The molecular dipole moment (File 4-3) is the vector sum of the individual dipole moments within the molecule. 

To filter a solution one attaches a vacuum and pours the solution into the Buchner funnel. All the solution will go whoosh into the flask leaving what is called a filter cake in the funnel. The liquid that has collected in the flask is now called the filtrate. Usually, the filter cake is then washed with a little bit of clean what-... 

Ether - Starting fluid (works great - Quaaaaack ) 2. Home made mercuric acetate (Now this stuff can be special ordered from ones chem supplier but there s a delay, may look funny - Quaaaaack , and is more expensive. So what is the solution to this Make it yourself Its easy, quantitative, and cheaper. Strike mentions this in the book and points ducks to a reference. Follow the EXACT same procedure for Mercuric Propionate except use glacial acetic acid...quack ). You ll need to use 20 to 25% more of the home brew mercuric acetate since it is a little contaminated with acetic (ducks can t get it totally dry without a vacuum oven). 3. NaOH washed Brazillian is fine Quack No need to purify further for starting material ... 

After 5 hours the reaction is stopped and the flask cooled. The formyl-MDA can be isolated and hydrolyzed by any of the ways Strike just mentioned a few paragraphs back, but this method offers a third, very convenient way which should be tried. What the chemist does is forget about letting the flask and its contents cool. Instead, she removes the oil bath, places the flask back on the stirplate (distillation setup still attached), attaches a vacuum and distills off all the formamide. What remains is a dark, heavy formyl-MDA precipitate that is allowed to cool down while the chemist makes up a solution of 150g potassium hydroxide (KOH), 500mL ethanol and 125mL dH20. This solution is poured into the... 

METHOD 2 [89]--1M MDA or benzedrine and 1M benzaldehyde is dissolved in 95% ethanol (Everclear), stirred, the solvent removed by distillation then the oil vacuum distilled to give 95% yellow oil which is a Schiff base intermediate. 1M of this intermediate, plus 1M iodomethane, is sealed in a pipe bomb that s dumped in boiling water for 5 hours giving an orangy-red heavy oil. The oil is taken up in methanol, 1/8 its volume of dH20 is added and the solution refluxed for 30 minutes. Next, an equal volume of water is added and the whole solution boiled openly until no more odor of benzaldehyde is detected (smells like almond extract). The solution is acidified with acetic acid, washed with ether (discard ether), the MDMA or meth freebase liberated with NaOH and extracted with ether to afford a yield of 90% for meth and 65% for MDMA. That s not a bad conversion but what s with having to use benzaldehyde (a List chemical) Strike wonders if another aldehyde can substitute. 

The chemist may have to do one, or possibly two more volume reductions before all of the excess ammonium chloride is removed (usually just one more). Now, what the chemist will be looking at after the last removal of ammonium chloride is a light yellow, slightly viscous solution that is about 1/3 the volume of the original filtrate. The chemist puts this to distill once more. What often happens next is that while the chemist goes off to watch TV the solution will distill off just a little bit of volume and poof the hot solution will become an instant mass of methylamine hydrochloride. If this doesn t happen for the chemist then she will just reduce a little bit and chill. Either way, what the chemist is going to have is a nice mass of methylamine hydrochloride crystals that she separates by vacuum filtration. 

This catalyst should really be purchased rather than made because its use in underground chemistry is limited and is hardly watched at all if not ever. This may change considering its potential as a precursor to the NaBHsCN in Strike s 1 method of choice. There are a lot of ways to make this catalyst, but the least involved is the one using boron trifluoride. What the method calls for is an apparatus called an autoclave. You know how using a vacuum causes the absence of pressure to make things boil at a lower temperature Well, an autoclave is a device that causes an... 

In any leaf test program there is always a question as to what vacuum level should be used. With very porous materials, a vacuum in the range of 0.1 to 0.3 bar (3 to 9 in Hg) should be used, and, except for thermal-drying apphcations using hot air, the vacuum level should be adjusted to give an air rate in the range of 450 to 900 mVm h (30 to 40 cfm/ft measured at the vacuum. 

Eirst of all, what is meant by a solid surface Ideally the surface should be defined as the plane at which the solid terminates, that is, the last atom layer before the adjacent phase (vacuum, vapor, liquid, or another solid) begins. Unfortunately such a definition is impractical because the effect of termination extends into the solid beyond the outermost atom layer. Indeed, the current definition is based on that knowledge, and the surface is thus regarded as consisting of that number of atom layers over which the effect of termination of the solid decays until bulk properties are reached. In practice, this decay distance is of the order of 5-20 nm. 

Product separation for main fractionators is also often called black oil separation. Main fractionators are typically used for such operations as preflash separation, atmospheric crude, gas oil crude, vacuum preflash crude, vacuum crude, visbreaking, coking, and fluid catalytic cracking. In all these services the object is to recover clean, boiling range components from a black multicomponent mixture. But main fractionators are also used in hydrocracker downstream processing. This operation has a clean feed. Nevertheless, whenever you hear the term black oil, understand that what is really meant is main fractionator processing. 

A hemispherical dome of 200 mm diameter has been vacuum formed from a flat sheet 4 mm thick. What is the thickness of the dome at the point furthest away from its diameter. 

Each of the vertical arrows in Fig. 1 represents the process of plunging one or more ions from a vacuum into a certain solvent. We want to know in detail what takes place in this process. For each ion in the final state a little portion of solvent is subject to the intense field of the ionic charge and is slightly modified. Thus each ion determines to some extent the character of its own environment in the solvent. In com-... 

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