d. **Example 4**. Determine the amount of serum in 40 mL of a 1:5 dilution of

serum with saline.

Solution. Read the problem carefully and use ratio and proportion to

determine the amount of serum in the given volume of solution.

1 part serum

x mL serum

------------ ------------

5 total parts

40 mL total

(5 total parts) (x mL serum) = (40 mL total)(1 part serum)

40 mL total)(1 part serum)

------------------------= x mL serum

5 total parts

x mL serum = 8 mL serum

Serial dilution techniques are used when it is necessary to test several

successive dilutions on the same sample. The procedure involves the preparation of an

initial dilution and subsequent redilution of aliquots (portions) to give progressively more

dilute solutions. In order to calculate the final or intermediate dilutions, use each dilution

of interest as a multiplicative factor, of which the resulting product is the dilution.

a. **Example 1**. A serum specimen was successively diluted 1:2, 1:2, and 1:2

with saline. What is the final dilution of the specimen?

Solution**. **When determining the final dilution of a series of dilutions use each

dilution as a multiplicative factor. The resulting product is the final dilution.

1

1

1

1

-- X -- X -- = -- or equivalently, 1:8

2

2

2

8

b. **Example 2**. A 1:10 dilution of a substance is rediluted 3:5, 2:15, and 1:2.

What is the final dilution?

MD0837

6-4

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