I am reading a fairly old paper today (1930), and they used a notation for concentration that I am unfamiliar with and can't seem to find info in Google about it. Here is the quote from the paper:

 

"The concentrations of caffeine (Merck U.S.P.) were M/500, M/750, M/1000."

 

Can someone tell me what M/500 means? Moles? Parts per million?

 

Thanks in advance.

I found a paper from 1928 that said

 

"The mixture was made

by adding 1 cc. of M/10 acetic acid to 50 cc. of the salt solution which gave a M/500 concentration of acetic acid without changing appreciably the concentration of the salt solution."

 

Is it possible to figure it out from that?

 

http://www.jgp.org/cgi/reprint/11/5/515.pdf

Hmmm... Could be fraction of mole? As in M/10 being 0.1 molar.

ecoli I saw that one too. But what is the concentration of M/10 acetic acid? Plus there is now a total of 51 cc's which leads to M/500? I am still confused.

M/500 is 1 mol per 500 litres

Thanks IA, I knew it had to be something simple. However, give me ppm or fractions of a mole per 1 liter anyday.

well think about it. there is 1/500 mol per litre then. just take the /500 as 1/500 and you have it in mol per litre.

I don't have a problem with conversion now that I know what it is, I am just saying it is a pretty awkward notational system (which is probably why I have never seen it before).

 

Consider, you want to mix two solutions together x parts M/5 and y parts M/10. x/5 + y/10 = 2x/10 + y/10 = (2x+y)/10.

 

That was an easy one. What if it was 3 part solutions? M/7, M/13, and M/17. You have to mulitply all those fractions out, or bascially convert it to decimal notation anyway.

 

And what do you do if the fraction cannot be converted into 1 over an integer? M/6.84 is really just using an awkward notation for notation's sake.

 

That's why I said give me moles per liter (I should have explicitly said in decimals) or ppm anyday, since you don't have to fool around with these wierd fraction and stuff.

fractions rule. i use them all the time as well as decimal. it can make calculations soo much easier sometimes. learn to love them.

I don't see what the big deal is.

Mathematically 0.001 is the same as 1/1000,

so 0.001 M is the same as 1/1000 M

Since multiplication gives the same answer whichever way round you do it 1/1000 M is the same as M X 1/1000.

Multiplication by 1 does nothing so you can leave it out and get M/1000