what is the hold time for pH measurements for water samples?
814606
pH samples need to be analyzed immeditely for regulatory purposes.  There is no holding time.  They must be test ASAP.
398743
Sometimes it does, sometimes it doesn't.  It depends how the data are being collected and processed.\n\nThe is an "unretained peak" delay time between injection of the sample and arrival of the first molecules from the injector to reach the detector device, whatever it may be.  Depending on the carrier gas, the column type & dimensions, and to some extent to carrier flow, it will take x amount of time for an unretained molecule to get from injector to detector.  The retention time is only a relative measurement anyway, for comparing standards to sample for identification purposes.  Hope this helps...
1017595
A standard solution is one that has been very carefully analyzed and characterized, usually by means traceable to a central standards bureau, such as NIST, so that the value is well known and can be trusted for instrument calibrations and methods development.\n\nA control sample uses known quantities of an analyte (it may be a standard, but does not have to be) so that analytical chemists can confirm that their processes are accurate and precise.\n\nFor example, I might have a standard buffer solution that I use to calibrate a pH meter on a regular basis, say daily.  Then, during each day, as I run dozens or hundreds of pH readings, I will periodically (say, once ever 20 tests), run a control sample through to make sure my readings are still in line with what I'd expect.  This gives the customer more confidence that the readings really match the real world situation.\n\nHope that helps.
865120
Hold up time is simply the time it would take for the tank to run empty if the incoming supply was suddenly cut off.\n\nSince the outgoing flowrate is 5 L/min, in 30 seconds, 2.5 litres would be needed.\n\nTherefore, you would need a vessel that has a volume of 2.5 litres.
224213
well, pH = -log[H+]. so if you just undo the log you will have the concentration of H+ (which is the same as H30+). then .. [H+} + [OH-] = 14 good luck!
904575
pH=-log(H+)\nthen H+ or H3O+ if done in water is:\n10^(-1*pH)\nFor plugging in 7.5 in above returns: 3.16 x 10 -8 M (molar concentration)\nsimilarly pH 9.6= 2.51 x 10 -10 M
1095569
check this link-- http://www.orgsyn.org/orgsyn/prep.asp?prep=cv6p0468.\n\ninstead of Me use Ph
48939
none water is H2O two parts hydrogen 1 part oxygen any thing else the water is inpure.but in the case of fish do a 1/4 water change every week so not to shock your fish make sure you keep temp about 78 degrees or they can get ick as far as testing you dont have to test fresh water but salt water is where the nitrite cycle is critical and then you also will test ph which is idealy 8 use a hydrometer to the line as it mesures the salt level by the boyency of the device nitites no higer than 14 i belive ask you pet shop owener as it been abuot 10 years since i had my salt water tank but for fresh water, the water change should cover it.
91904
That depends on the type of pH stripe. They come with a color scale so you can compare the color with the standards.
966389
Because it is quite a mild solution. There's plenty more water than acid, therefore you may assume that the properties of the water haven't changed much.
573222
Once a solution of HCl hits pH 7, it is considered neutralized (or in other words it'll basically be water.) After a pH of 7, a solution has to be alkaline (or basic,) which an acid cannot be.
1073643
the easiest way is to use a pH paper to test the pH. and just compare the reading with the one given with the test kit. \n\nOr you may do some neutralisation. And then calculate with the  amount of alkali you use for neutralisation. By that you can calculate the concentration of hydroxide ions in the alkali that you use. Then calculate the pOH for the alkali you use. pH=14 - pOH.\neg. \n1mol of NaOH gives you 1 mole of OH ions.\nso the pOH = -log1 = 0\npH = 14 - 0 = 14\n\nJust some rough guide. Hopefully it helps...Good luck.
682738
There is a product made by HTH called pH Minus. (I'm sure there are other company's that make it as well), it's fairly inexpensive, around $14.00 for 1/2 gal. Just follow the directions and your water will be back to normal in no time at all. It works quickly! GOOD LUCK!
553835
Well to determine [H+] you use the equation that \npH=-log [H+] \nthus a solution with pH=3 will have a [H+] of 1x10^-3, \nand a solution with pH=8 will have a [H+] of 1x10^-8\nTo find [OH-] there are several equations you can use\n[OH-]=Kw/[H+], \nKw is the ionization constant of water which is equal to 1.0x10^-14\nThus you will have [OH-] of 1.0x10^-11 and 1.0x10^-6\nSo you answer will be that the solution with pH=3 will have a [H+]>[OH-]
650541
pH = -log ([H3O+])\npOH = -log ([OH-])\n\npH + pOH = pKw = 14\npOH = 14 - pH\n\n[OH-] = 10^-(pOH)\n\nPlug in and solve.
133368
Normal ph level is 7.35-7.45
482772
Ph is A measure of the acidity or alkalinity of a solution, numerically equal to 7 for neutral solutions, increasing with increasing alkalinity and decreasing with increasing acidity. The pH scale commonly in use ranges from 0 to 14.