1. Preparation of Solutions (cont.) Procedure Checklist 6-1: Procedure Checklist 6-1: Calculating by the Proportion Method 1. Write a conversion factor with the units needed in the numerator or before the colon; units converting from in the denominator or after the colon.

2. Preparation of Solutions (cont.) Procedure Checklist 6-1: (cont.) 2. Write a factor with the unknown, “X,” in the numerator or before the colon. with the number to convert in the denominator or after the colon. X / B or X:B

3. Procedure Checklist 6-1: (cont.) 3.Set the two factors up as a proportion. 4.Cancel units. 5.Cross-multiply or multiply the means and extremes and solve for the unknown value. Using Conversion Factors: Proportion Method (cont.) X / B = C / D or X:B = C:D

4. Preparation of Solutions (cont.) Calculate the amount of NaCl needed for for 250 mL of 0.9% sodium chloride. 0.9 g NaCl in 100 mL solution Step A Convert No conversion is needed. Example

5. Preparation of Solutions (cont.) 0.9 g NaCl in 100 mL solution Step B Calculate using the proportion method. 0.9 g / 100 mL = X / 250 mL 0.9 g x 250 = 100 x X 225 g / 100 = 100X / 100 2.25 g NaCl = X Example

6. Preparation of Solutions (cont.) Step C Think!...Is It Reasonable? Since there is 0.9 g of NaCl in 100 mL, there should be more than 2 times that amount in 250 mL, so 2.25 g is a reasonable answer. Example

7. Preparation of Solutions (cont.) Procedure Checklist 6-2: Procedure Checklist 6-2: Calculating by Dimensional Analysis 1. Write the unknown “X” on one side of the equation. X =

8. Preparation of Solutions (cont.) Procedure Checklist 6-2 (cont.) 2. On the other side of the equation, write a conversion factor with the units of measure for the answer on top and the units you are converting from on the bottom.

9. Preparation of Solutions (cont.) Procedure Checklist 6-2 (cont.) 3.Multiply the numerator of the conversion factor by the number that is being converted divided by 1.

10. Preparation of Solutions (cont.) Procedure Checklist 6-2 (cont.) 4.Cancel units.

11. Preparation of Solutions (cont.) Procedure Checklist 6-2: 5.Solve the equation.

12. Preparation of Solutions (cont.) Step C Think! … Is It Reasonable? Regardless of the method used, we find that 2.25 g of NaCl is needed to prepare 250 mL of a 0.9% solution. Example

13. Preparation of Solutions (cont.) Write the recipe for 250 mL of 0.9% sodium chloride solution. Example 0.9% Sodium Chloride Solution NaCl 2.25 g Water qsad 250 mL

14. Practice Write a recipe for preparing 50 g if a 10% zinc oxide ointment using zinc oxide powder and petrolatum jelly. ANSWER: 10% Zinc Oxide Ointment Zinc oxide powder5g Petroleum jelly 45 g

15. Preparing a Dilution from a Concentrate When preparing a solution from two solutions of different concentration, know –Solvent – less concentrated solution –Solute – more concentrated solution To calculate, use –Formula method –Alligation

16. Preparing a Dilution from a Concentrate (cont.) Procedure Checklist 16-1 Formula Method 1.Identify information needed: a.V = volume of solution needed b.C = concentration of solution needed c.St = amount of solute d.Sv = amount of solvent

17. Preparing a Dilution from a Concentrate (cont.) Procedure Checklist 16-1 Procedure Checklist 16-1 (cont.) 2.Insert values into formula: C x V = St 3.Determine the amount of solvent by subtracting the solute from the total volume: V – St = Sv

18. Preparing a Dilution from a Concentrate (cont.) Ordered: 1 oz of ¼ strength hydrogen peroxide in normal saline for wound care TID for 2 days. Write the recipe. Step A = Convert ounces to mL. 1 oz TID x 2 day = 6 oz 1oz/30 mL = 6 oz/ X 180 mL = X Example

19. Preparing a Dilution from a Concentrate (cont.) Step B Calculate. V = 180 mL, C = ¼ C x V = St ¼ x 180 mL = 45 mL of the solute (hydrogen peroxide) V – St = Sv 180 mL – 45 mL = 135 mL of the solvent (normal saline) Example

20. Preparing a Dilution from a Concentrate (cont.) The recipe is: Step C Since 45 is one fourth of the total volume of solution (180 mL) and 135 + 45 = 180 mL, this answer is reasonable. Example ¼ strength Hydrogen Peroxide – 180 mL H 2 O 2 45 mL NS 135 mL

21. Practice Clean leg wound with 2 oz of ½ strength hydrogen peroxide in normal saline q6 h x 3 days. Write the recipe for total supply needed. ½ hydrogen peroxide – 720 mL H 2 O 2 360 mL NS 360 mL ANSWER: