Createing stocks of KH2PO4

Gilles

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Aug 6, 2008
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Anybody can help me with how to calculate how many milligrams i need to add to achieve the following stocks?

0.25 mg/l KH2PO4
0.50 mg/l KH2PO4
1 mg/l KH2PO4
2 mg/l KH2PO4

The grams would be dilluted in 500ml anion water to test a fotonmeter.
 

Riba

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Feb 14, 2006
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Mmm, I'm afraid that that's not gonna work (if I properly get what you want).

In order to get 500 ml of water with 0.25 mgPO4/l out of KH2PO4, you'd have to add 0.179 mg (0.25/2 * 1.432) of KH2PO. Then think of how accurate you can measure (both the powder and the water).
For the rest, doubling the (milli)grams will do ;)

Mmm, isn't this dutch calculator yours (I might be mistaken)? You can use it to check my calculation... ;)

If you'd insist proceeding as above, you could make a 2mg/l solution (so 0.179*2*2*2 = 1.432 mg KH2PO4 in 500 ml water). Then split the stock in half, and add 250 ml of water to one of the parts. This one will be the 1 mg/l solution (the other one will stay the 2mg/l solution). In same way, split and dilute the 1mg to 0.5 mg/l and subsequently to 0.25 mg/l

In any way, try to assess your accuracy/error, also in case you decide to make a bigger batch...

Groetjes,
Riba
 
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Riba

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Hi Gilles,

Any thoughts on how you are going to approach this?

Grzt,
Riba
 
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