[wils0645]

If I wanted to create a solution (diluted with water-total volume of 2000 mL) with final ion concentrations (in mM): Na 150, K 3.0, Ca 1.4, Mg 0.8, P 1.0, and Cl 155, what compounds should I buy and how would I mix them?  I am not a chemist so I do not know if any of the compounds are hazardous when mixed with H2O.

My answer:  The easy one is NaCl...I have a large tub full...I don't need to buy this
I have 100 g of MgCl, says on the bottle it has a very exothermic reaction with H2O
I need to buy KCl and CaCl2 as well?  How would I incorporate Phosphorus?  Maybe PCl3?

For NaCl, at 150 mM and 155 mM respectively, I would need to add 150 mmol/liter or .30 mol for 2000 mL and .31 mol for 2000 mL.  Therefore, I would add 6.8969 g Na and 10.9904 g Cl, or .306 mol (17.8873 g) NaCl?  How would I dilute the compounds to a final ion concentration shown above (Na 150, K 3.0, Ca 1.4, Mg 0.8, P 1.0, Cl 155)?

[Arkcon]

If you're preparing a nutrient solution for some living things, i.e. hydroponic media for plants or a microbial culture medium, you can get phosphorus from a number of salts, for example potassium dihydrogen phosphate, which will address both potassium and phosphorus, if your application is appropriate.  The calculations required, are not difficult, but they are lengthy -- it would be a lot of grinding, on paper, for me at least.

Two things:

Your specific application: is this plant food, hydroponic media, microbial media, or some chemical application I haven't guessed?  We need to know this info to give you good information.

Consider that, since you lack the specific chemical training, that you might want to see if you can acquire the media you need pre-mixed from a vendor.  We often have to explain the concentration of one salt mixtures to new students again and again, before they begin to follow it, and they have real incentive -- learning this stuff is their job, while in school.  We'd have too much to teach you, message by message.

[wils0645]

Thanks for the response.  My specific application is to create an electrolyte solution similar to cerebrospinal fluid.  I can buy artificial CSF from several vendors, but it is very expensive (ie $250 for 150 mL).  I graduated from college last year in biomedical engineering and took a semester of introductory chemistry.  A small sample calculation would be fine if you're willing to help:

Let's say you need 150 mM Na.  How many moles of NaCl would I need to achieve this?

2Na + Cl₂<----->2NaCl
So would I need 150 mM NaCl to achieve this?

Thanks.

[Arkcon]

2Na + Cl₂<----->2NaCl
So would I need 150 mM NaCl to achieve this?

Thanks.

OK, your vendor's formula lists it's ionic concentration as Na, Cl, etc.  These are not elemental concentrations, so you can drop, right now, the formula above.

Therefore, I would add 6.8969 g Na and 10.9904 g Cl, or .306 mol (17.8873 g) NaCl? 

You can, of course, add the elements, like you list above, to water and get the correct concentration.  But that is just silly.  Sodium is dangerous, and you can't really weigh out chlorine gas, and stir some in.

This synthetic cerebrospinal fluid is, in some way, a derivative of human Ringers solution.  It is, most likely, a mixture of sodium chloride, potassium chloride, magnesium chloride and calcium chloride, and potassium phosphate. These simple, cheap, safe, very soluble, ionic salts are mixed, such that the elemental compositions of the salts add up to the elemental composition on the label.

But the label's not the whole story.  That's just a blurb so they can give you just enough info that you can't easily mix it for yourself.   Elemental phosphorous concentration, for example, won't matter, as much, to a living thing as the ionic concentration.  Incorrect osmolality will kill cells.  Your composition gives no mention whatsoever of pH, another important quality.

Look up on Google for synthetic cerebrospinal fluid.  Maybe some university has posted a recipe.  Or, try calling a university lab.  They tell you what masses of what salts to use.

Oh, and don't use the MgCl2 that says it gives an exothermic reaction with water, that is the anhydrous form, for drying solvents.  The recipe will say to use the hydrated form, and the amount will be tailored for that form.  And PCl3 is, likewise, too dangerous a form to use for cerebrospinal fluid.

[wils0645]

Thanks for your help Arkcon.  I appreciate it.

[Arkcon]

Thanks for your help Arkcon.  I appreciate it.

No problem.  You will also have to add something like plasma proteins, 0.3%, which I got from wikipedia.  If this is some sort of electrical or physical application, you can mimic that with bovine serum albumin, a cheap soluble protein.

*[EDIT]*

Hey, look over here, http://www.cerebrospinalfluidresearch.com/home/
They have browseable abstracts.  Maybe one will have a recipe for you.

And over here is the complete text of a patented synthetic cerbrospinal fluid: http://www.patentstorm.us/patents/6500809-description.html
Now they don't give the exact formula either, because they don't want anyone stealing it.  But there's lots more information there, like the addition of glucose, to nourish cells, and some of the Na+ is provided as bicarbonate, which is also important for cells.  Lots of stuff for you to learn.