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µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 1:46 AM

Please help on this matter which belongs to soluble salt contamination on blasted pipe,

Up to 10ppm is acceptable as per specification but the reading coming in µS/cm by the conductivity meter (Elcometer model B-173) while checking, It was our mistake to convert µS/cm into µg/cm.square (as shown below in hi-lighted) and considered it equivalent to PPM, But after going deep in matter there is no compatibility between µg/cm.square and PPM because PPM references mass density whereas milligrams per square centimeter is for surface density, means converted reading of salt contamination was in µg/cm.square and the same reported on thousands of paper as in PPM which is recommended in specification, Is there any relation between µg/cm.square to PPM??, Pl.guide me to resolve this issue,

Previously Belzona also declared that µg/cm.square is equivalent to PPM which is revised now,

For example as per instruction manual, µS/cm x 0.11 = µg/cm2

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#1

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 3:29 AM

Context?

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#2
In reply to #1

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 4:27 AM

http://www.m-testco.com/specialty-tools/water-testing/horiba-b-173-conductivity-meter-p-1615.html

Specification recommended unit is PPM but the model of instruments we used (click on above link) is coming in microgram/cm.square after conversion from mS/cm as specified previously,

Is there any compatibilty between PPM to mS/cm or microgram/cm.square????

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#3
In reply to #2

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 4:44 AM

None whatsoever. mS/cm is the conductivity of a fluid whereas microgram/cm.square is a coating thickness on a solid.

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#4
In reply to #3

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 4:53 AM

Is there any compatibility with mS/cm to PPM because PPM is also conductivity of a fluid?

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#5
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Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 5:24 AM

At typical nothern hemisphere room temperatures, the ratio between μS/cm and PPM total dissolved solids is in the order of 3 to 2. It is strongly affected by temperature changes.

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#6
In reply to #5

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 5:43 AM

Pl. if reading is 50mS/cm then by considering this ratio (3:2) how much will be in PPM, Is this ratio specified in any standard?

Thank you very much for your support

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#7
In reply to #6

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 6:16 AM

That level of water quality represents either RO reject water or non-estuarine seawater from close to the equator.

The arithmetic is trivial and there is no standard; it is an empirical thing - a "rule of thumb" used locally. It will not apply in higher temperatures.

'Total Dissolved Solids' in PPM is a generalised measurement of water quality. If more detailed, ion-specific figures are required then analysis of samples in a laboratory is the way forward.

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#8
In reply to #7

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/08/2012 6:21 AM

Thanks again

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#9

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/09/2012 3:56 AM

My understanding is

PPM is parts per million which is a quantity

µg/cm.square is micrograms per cubic centimeter or more commonly expressed as ug/cc which again is a quantity. one millionth (1/1000000) of a gram (1 × 10−6), or 1/1000 of a milligram

Similar description to PPM

From wiki;

µS/cm The siemens (symbol: S) is the unit of electric conductance and electric admittance in the International System of Units (SI). Conductance and admittance are the reciprocals of resistance and impedance respectively, hence one siemens is equal to the reciprocal of one ohm, and is sometimes referred to as the mho.

end of wiki

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#11
In reply to #9

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/09/2012 12:51 PM

'µg/cm.square is micrograms per cubic centimeter'

NO!

µg/cm.cubed is micrograms per cubic centimeter

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#10

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/09/2012 12:20 PM

This should help:

http://www.appslabs.com.au/salinity.htm

As others have said, ug/cm sq. has no real meaning, except as a measure of coating on a surface.

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#12

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/09/2012 3:22 PM

Actually μg/cm2 is a measure of pressure and does not relate to conductivity. As PWslack points out the use of conductivity to convert to mg/L or ppm is an empirical calculation and should only be used as a guide to those familiar with the water characteristics. The ratio is affected by temperature. Conductivity is reported by labs at a standard measured at 25 degrees C. For example if the water were 10 degrees C you would have to multiply your measured conductivity by a factor of 1.42. At a temperature of 35 degrees C you would have to multiply the measured conductivity by 0.83. Generally, the temperature/conductivity are affected by about 2%/degree C change. Charts are available.

Another factor is that all ions do not contribute to conductivity in a uniform manner. For example, if sulphate ion (SO4--) is a dominant anion, your conductivity can read very low compared to real TDS. For most water in the potable range of conductivity, you could multiply the conductivity by 0.5 to 0.66 but it can still vary. For "salty" water, as you have indicated, the measured conductivity may be multiplied by as high as 0.9. In order to familiarize yourself with the water, I would bring many samples over a period of time and have an accredited lab do both the conductivity and TDS measured as per a standard method. You may collect enough information to guide you in the conversion after a year or more off collecting data. Remember conductivity is meant to be used as a guide and not an indcation of water analysis. Hope this helps.

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#13
In reply to #12

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/10/2012 2:17 AM

Thanks a lot to all of you for valuable comments, I have already been send an inquiry to kit manufacturer (HORIBA) for this case, still result is awaited because EC multiply by factor as above (Mr.Kevinm) is also out of our acceptable limit which is 10PPM

ppm (parts per million) is the most commonly used scale to measure TDS (Total Dissolved Solids).

µS (micro-Siemens) is the most commonly used scale to measure EC (Electrical Conductivity).

---------------------------------------------------------------------------------

As previously mentioned the conversion from µS/cm to µg/cm2 which was from manufacturer instruction manual of instrument, Details of instrument as below

HORIBA LTD

TWIN COND, Conductivity Meter B-173

Serial No.: 912412

But now going to use short cut, reading as coming on meter is in µS/cm, just multiply by 0.640 to get value in PPM TDS as per this link http://www.lenntech.com/calculators/conductivity/tds-engels.htm

TDS and Conversion Factors as per this link is http://www.tdsmeter.com/what-is?id=0019

TDS: NaCl 0.47 to 0.50

TDS: KCl 0.65 to 0.85

TDS: 442 0.50 to 0.57

Converting between different scales, multiply the above factor to EC to get the value in PPM TDS,

Horiba173.PDF

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#14
In reply to #13

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/10/2012 10:12 AM

As others have pointed out above, different ions will affect the conductivity differently (for the same concentration). So if you are looking for a conversion between conductivity and TDS, my suggestion is to create your own standards (rather than putting your trust in some arbitrary calculator on the web).

If you know the relative proportions of the types of salts you are trying to measure, then creating an accurate standard is simple. Once you have the standards you can find the right conversion for your particular samples and have proof that the numbers you come up with are valid.

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#15
In reply to #13

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/10/2012 3:15 PM

This from your B173 specs:

B-173

Packed with advanced features!

Features

  • Auto-ranging and a measurement range from 1 µS/cm to 19.9 mS/cm.
  • One-touch auto-calibration.
  • Automatic temperature conversion.

Your meter has auto temperature compensation. You must leave the tip of the meter in the water for about 2 or 3 minutes gently swirling it to allow the meter to read the temperature. You also may want to use a calibration solution to get high and then a low range. Also do not read a salt water and then try to read a low conductivity. Be sure to rinse your probe with DI water if you are trying to read salty then fresh water or better get two separate probes. Calibration is important and may have to be done frequently depending on how you are using the B173.

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#16
In reply to #15

Re: µg/cm.square Vs. PPM (Soluble Salt Contamination)

05/17/2012 2:32 AM

Thanks Mr.Kevinm to express the operation of meter (B-173) which we used, Belatedly reply because I was away from my system for couple of days

Thanks a lot

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