11:54 Oct 27, 2011 

Sorry you're right "l" is not the SI unit, of course the unit is the metre, 'length' (and 'l') is the dimension. Most of my professors wouldn't care if you use 'l' for litre but my supervisor was very strict about it and to be honest it is good standard practice.
mg has to for milligram otherwise 'l' has no sense on its own.
@ David - ppm is only realyy typical when talking about water, in the lab we would use molarity or mg / L.

15:43 Oct 26, 2011 

mg/L is milligrams per liter, not magnesium...

15:42 Oct 26, 2011 

The exact measurements are 1.6 in one case and 1.9 in another. I agree with DrNeil in as far as I can't see what calcium has to do with oil and grease. However it's not hydrocarbons as that is another measurement elsewherer in the table. Basically it's a series of tests on seawater pollution (or lack of)

11:47 Oct 26, 2011 

Both Ca and Mg can also be expressed in mg/l
And "length" is not a standard SI unit. The unit for length is m (meter). I have learned mg/l as miligram per liter. But I agree that L is a better option. Holmsie, if you have a figure for this item, please send it.

10:11 Oct 26, 2011 

I'm sorry if I didn't ask clearly enough, but could you please tell us what the actual measurement given for this value is?

06:35 Oct 26, 2011 

I would say that it refers to calcium AND magnesium as the unit in these cases is, usually, parts per million (ppm).
en.wikipedia.org/wiki/Hard_water--Recommendations have been made for the maximum and minimum levels of calcium (40-80 ppm) and magnesium (20-30 ppm) in drinking water
www.lenntech.com › Periodic table › Elements and water
Magnesium is present in seawater in amounts of about 1300 ppm. ... contains magnesium, for example dolomite (calcium magnesium carbonate; CaMg(CO3)2) ..

19:55 Oct 25, 2011 

I agree with the capitals for the first letter of the elements in question. Very shoddy work indeed if proved to be Ca and Mg. I just wanted to make sure Holmsie checked the source text properly.

19:49 Oct 25, 2011 

And yes it is a very poor source if ca is for calcium, when it should definitely be Ca, as Ana states.
And "l" (the letter not the number 1) is length, standard SI unit. A good scientist should always have been taught to use L for litre.

19:20 Oct 25, 2011 

both for Ca and Mg a capital is required in case they refer to calcium and magnesium. For liters, the capital is a recommendation, not mandatory

18:20 Oct 25, 2011 

If the measurement referes to the amount of oil and greae why does everyone think that Ca is calcium???? Where is the reference to oil and grease?

Admittedly I have no idea, I would expect something along the lines of HC (hydrocarbon) - mg/lt.
Either way the IUPAC standard for LITRE (US - LITER) is L , capital L to avoid confusion with the number 1. Normally only units named after people are given a capital letter but litre is a special case for this reason. Thats my showing-off done....

14:54 Oct 25, 2011 

for this value? mg could be magnesium which, along with calcium, is what causes hardness in water. But it could also be milligrams indicating concentration of calcium as a measure of hardness.

13:50 Oct 25, 2011 

Is it not calcium? And make sure mg is not magnesium as both are common in seawater