I'm having trouble with this algebra - can anyone out there explain it in words? I'm listening to the recording, but it still escapes me.

thanks very much - i'm at a complete standstill because i don't understand this!

Mary

Comments

Sat, 06/18/2011 - 20:08

dancingfish (not verified)

I'll try.   This is the formula for dye stock, where given a DOS percentage (in this case 2%), Karren is showing how to calculate how much dye (determined to be 0.08g) needs to go into a given volume (4mL) in the first line.  E.g. if you want to make 4mL of dye stock at 2% DOS, then you would use 0.08g of powder dye.  Then she takes the same formula and shows how you can also calculate, from a given amount of dye, how much dye stock volume you can make.   E.g. if you have 0.08g of dye, and you want to make DOS 2%, you can make 4mL of dye stock.

Does that help?  Maybe Karren can clarify if that's not what she was trying to get across.

Linda

 

Sat, 06/18/2011 - 20:22

dancingfish (not verified)

Okay, so now I have a question.  I think this formula doesn't have anything to do with DOS %.  So the 2% is not about DOS, but is what we need to use to make stock solution from Cibacron.   The formulas still calculate the same thing, but the percentage is always 2% for Cibacron..  Is that right?

Sorry, Mary, I hope I'm not confusing you.

Sat, 06/18/2011 - 22:04

Hestia

2% is not about DOS.  It represents a 2% dye stock solution  (2 grams of dye in 100ml of water).  She's calculating how much of this 2% stock solution she needs to use to give her the 0.08g of dye that she needs for her project.

Calulate the amount of dye:

For her project she has determined she needs 0.08g of dye (from the following formula).

WOF(g) x DOS (%) = amount of dye needed (g)

5.1g x 1.6%  = ?

5.1g x 0.016 = 0.08g of dye

Problem is she wants to dye something and needs 0.08 g of dye.  You can't measure that amount of dye on a balance.  Therefore, you make a 2% stock solution to get the small amount of dye needed 0.08g.  Now she wants to know how much of this 2% stock solution she needs to give her the 0.08g of dye she needs for her project.

First, she's looking at the chart 'Calculating dye in stock'.  She looks in the last column, 'Amount of dye contained' and sees 0.05g and on the next line 0.10g.  She knows she needs 0.08g dye for her project which is between these two.  She next looks in the 'volume' column and sees 2.5ml and the next line 5ml. She's initially guessing that 0.08g is equal to 4ml volume of the 2% stock solution.

 

2% (stock solution) x 4ml (volume) = 0.02 x 4ml = 0.08 ml = 0.08g dye

Therefore,  2% stock x ? = 0.08 ml (ml =g)

               2% stock x Vml = 0.08ml

solving for Vml:   ( how much of the stock solution she needs)

     Vml = 0.08ml/2%

     Vml = 0.08 ml/0.02

     Vml = 4ml

She now proves she needs 4ml of the 2% stock solution to get the 0.08 g of dye she needs for her project.

To get a bit more technical she's using the formulas below and replacing WOFg x DOS (%) which she knows is = 0.08g

Two Formulas:

WOFg x DOS (%) = g of dye powder  (which we know = 0.08g for the project)

WOFg x DOS(%) /stock (%) = ml stock

0.08g/2 (%)stock = ?  we need 0.08g of dye and using a 2% dye stock solution, how much do we need of the stock solution?

0.08g/.02 = 4ml    Now we're back to where we were before using these two formulas.

 

Hope this helps.

Sat, 06/18/2011 - 22:45

Mary Rios (not verified)

I'm thrilled there are major brainiacs in class! Thank you so much for your definitions - i'm printing them out and saving them! I worked with Karren earlier this afternoon and she helped me with my goesintos.

Hopefully there will be no more algebra...

Thanks again for taking the time to help me

Mon, 06/20/2011 - 17:32

Anne Vincent

goesintos???

Donna - excellent explanation!