How does one determine if precipitaion is comlete? Why is it important?
91636
Based on one of my chem classes:\n\nA reaction goes to completion if:\n>there's a precipitate.\n>one of the product is a gas and the system isn't isolated.\n>conditions are kept constant.\n\nI think the 'precipitation' you are asking is a 'precipitation reaction'. This effect is useful in many industrial and scientific applications whereby a chemical reaction may produce a solid that can be collected from the solution by various methods (e.g. filtration, decanting, centrifuging). Precipitation from a solid solution is also a useful way to strengthen alloys.
109204
it's all a bit relative since these days we also have "k"-value which is essential in forecasting precipitation.  it refers to the lift in areas of an airmass. for example, a thunderstorm can form, grow to 40,000 feet, drop its precipitation and go away in only a few minutes.  an area such as this would have a negative value for k, say minus 40 while a very stable area could be plus 40.  while the factors you refer to are important and useful indicators, consider that you can have any combination of humidity and pressure trend and it does not necessarily nean it will rain.  those parameters are the basis of centuries old meteorology and the principles have not changed all that much over time but then the forecasts delivered with these tools were marginal, at best.  the relationship principles you speak of were the basis for a guage to do precisly what you speak of. it's called a barometer and you can find all kinds of information on one on these any even probably find one to purchase for only a few dollars on e-bay or something. a borometer takes pressure trends, considers humidy and does give an estimated time in which precipitation would be expected.  accurancy?  well if i remember right only maybe about 60% or so but don't quote me there.
796939
Process Issue.\n\nThe Metal prior to Plating must be free of all contaminants.\n\nHave the Process and quality staff examine the Brass prior to the Plating and do a Controlled experiment with a sample size run.\n\nPerhaps a contaminate is entering the Process at a stage in the Handling of the Brass.\n\nProcess control must be verifiable at all times.\n\nClosing down the Line is costly and very expensive. But, The Product that the customer receives must be defect free.\n\nPlease review the following URL:\n\nhttp://www.finishing.com/96/76.shtml\n\nContact me by email, if I can offer addition assistance.\n\n\nRegards.
791931
Precipitation:: Precipitation is the formation of a solid in a solution during a chemical reaction. When the chemical reaction occurs the solid formed is called the precipitate. This can occur when an insoluble substance, the precipitate, is formed in the solution due to a reaction or when the solution has been supersaturated by a compound. The formation of a precipitate is a sign of a chemical change. In most situations, the solid forms ("falls") out of the solute phase, and sinks to the bottom of the solution (though it will float if it is less dense than the solvent, or form a suspension).\n\nThis effect is useful in many industrial and scientific applications whereby a chemical reaction may produce a solid that can be collected from the solution by various methods (e.g. filtration, decanting, centrifuging). Precipitation from a solid solution is also a useful way to strengthen alloys.\n\nAn important stage of the precipitation process is the onset of nucleation. The creation of a hypothetical solid particle includes the formation of an interface, which requires some energy based on the relative surface energy of the solid and the solution. If this energy is not available, and no suitable nucleation surface is available, supersaturation occurs.\n\n\n\nAggregation::Particle aggregation in materials science is direct mutual attraction between particles (atoms or molecules) via van der Waals forces or chemical bonding.\n\n\n\nCoagulation::The transformation of liquid into jelly like semisolid mass.\n\n\nFlocculation::Flocculation refers to a process where a solute comes out of solution in the form of floc or "flakes." The term is also used to refer to the process by which fine particulates are caused to clump together into floc. The floc may then float to the top of the liquid, settle to the bottom of the liquid, or can be readily filtered from the liquid.
826531
tiny amounts of chemical can stick to differnt things, like stir bar, stir rod, thermometer and if you remove these items before the experiment is over then you remove some chemicals.  Other kinetics events that your not considering. as in pressure, humididtym and so on.  If you used a Ph probe then maybe it wasn't calibrated right or isn't properly maintained
38065
There are innumerable soluble salts of organic and inorganic compounds. For some soluble salts, there will be no precipitate when sodium hydroxide is added. You can consider sodium acetate as one example of this but there are many many others. \nFor some soluble salts, there will be a precipitate when sodium hydroxide is added to solution. The appearance of the precipitate depends on the nature of the salt. For some soluble salts, such as ammonium hydroxide, the addition of sodium hydroxide will evolve ammonia as a gas. That reaction is part of the classical determination of protein in nutritional laboratories.
585752
Are you trying to perform a destructive or a non-destructive test. The formulas for both are different, and it would be difficult to advise without knowing...
740416
Your question is incomplete.  What type of stains are you talking about?  Looking at the properties of the stain and you may find the answer you need.
359177
Before a formal investigation you might do some preliminary checking around to verify that what someone's telling you is worth investigating further.\n\nIs this what you mean? (Unclear question.)
686279
You hear or read the latest weather forecast and it says "it's going to rain," and you want to know when, where, and how much; but instead, you are just given a probability of precipitation, a POP. What is this percentage? What does it mean? \n\nPOP is described as the probability that measurable precipitation, amounts greater than 0.01", will occur at a specific point, or rain gauge, in a specific period of time. \n\nFor example, the meteorologist says there is a 60% chance of rain today. According to National Weather Service policy, it means at any given point in the forecast area, including your backyard; there is a 60% chance that rain will occur. Another way of looking at it is, out of 100 days identical to today, on 60 of them, rain will occur. \n\nSometimes, more descriptive wording is used to lend additional meaning to the probability of precipitation in the forecasts. This wording explains the uncertainty and areal qualifiers, respectively. For example, a 10-20% chance of showers means there is a SLIGHT CHANCE of showers, or the showers would be isolated or widely scattered. Now, a 30-50% chance of showers means there is a CHANCE of showers, or the showers would be scattered. A 60-70% chance of showers means showers are LIKELY, or the showers would be numerous. While, a 80-100% chance of showers means it is current or very likely to happen. POPs do not necessary pertain to the intensity of the precipitation.
946141
Please call the lab where you'll have the test done and ask this important question.  Good luck.
1035950
The basic check is: measure the mass, divide by the volume of water displaced, check that the density is correct. After that you should still do a chemical analysis to make sure there aren't other heavy metals, like uranium or lead mixed in.
912005
It is the fluid like stress before it hardens.  It is important for use in designing form works so they don't blow out.  It is more than double that of water.
149433
If you are filling it, you have half filled it.\nIf you are drinking it, you have half emptied it.\nIf you don't know if it was last being filled or emptied, you can ususally safely assume someone was drinking from it and that they left it behind.
517995
67.  AgCl <---> Ag+ + Cl-  Ksp = [Ag+][Cl-] = 1.8 x 10^-10\n[Ag+] = 0.001/2 = 0.0005 M; [Cl-] = 0.0025 M; [Ag+][Cl-] = 1.25 x 10^-6, as this is greater than Ksp, a precipitate will form.\n\n68.  SrCrO4; Ksp = [Sr2+][CrO42-] = 3.5 x 10^-5; molar solubility = [Sr2+] = [CrO42-] = sqrt (3.5 x 10^-5) = 0.0059 M\n\n69.  Total volume = 3L  [Fe2+] = 0.150 * 1/3 = 0.050M; [OH-] = 0.0333 * 2 / 3 = 0.0222 M.  Ksp Fe(OH)2 = 4 x 10^-38.  (0.050) * (0.0222)^ 2 >>> 4 x 10^-38, so a precipitate will form.\n\n73.  Pb3(AsO4)2 <---> 3 Pb2+ + 2 AsO43-.  If solubility = x, then [Pb2+] = 3x, [AsO43-] = 2x.\n4.0 x 10^-36 = [3x]^3[2x]^2 = 108 x^5 ==> x = 3.26 x 10^-8
231862
How about Enzymatic Yield Optimization?  You might also use Enzymatic Precipitate Optimization if the result is a precipitate.
963001
First of all you should give us more info, like what exactly is the elimination test, concentrations, conditions and if you know the pH of the final solution or the final concentration of acetic acid.\n\nA very rough explanation based on the limited info, would be that HF is a much stronger acid than HPO4-2, so in an acidic environment it manages to dissociate much better, giving the conjugate base or if you prefer the conjugate base F- is much weaker than PO4-3 so PO4-3 will steal away the H+ from the acetic acid. Thus it is possible that in the acidified medium you have most of the phosphate in the form of HPO4-2, and the concentration of PO4-3 is too low to lead to precipitation.\nOn the other hand, although CaF2 is much more soluble, most of F- will remain as such and thus its concentration might be high enough to promote precipitation.