On concentration notation M/500?

[Bignose]

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.

[ecoli]

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

[Gilded]

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

[Bignose]

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.

[insane_alien]

M/500 is 1 mol per 500 litres

[Bignose]

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

[insane_alien]

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.

[Bignose]

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.

[insane_alien]

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

[John Cuthber]

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