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Pharmaceutical Calculations: Density, Specific Gravity, and Pharmaceutical Calculations: Density, Specific Gravity, and

Pharmaceutical Calculations: Density, Specific Gravity, and - PowerPoint Presentation

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Pharmaceutical Calculations: Density, Specific Gravity, and - PPT Presentation

Danielle DelVillano PharmD Objectives Define density specific gravity and specific volume and determine each through appropriate calculations Apply specific gravity correctly in converting weight to volume and volume to weight ID: 495240

weight specific volume gravity specific weight gravity volume water oil plummet glycerin chapter density problem weighs displaced substance equal

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Slide1

Pharmaceutical Calculations: Density, Specific Gravity, and Specific Volume

Danielle DelVillano, Pharm.D.Slide2

Objectives

Define density, specific gravity, and specific volume and determine each through appropriate calculations

Apply specific gravity correctly in converting weight to volume and volume to weightSlide3

Density

Mass per unit volume of a substance

Most often expressed as

g/mL

Density =

Mass

VolumeSlide4

Density Example

If 10

mL

of sulfuric acid weighs 18

g

, what is its density?

Density =

18

g

10

mL

= 1.8

g/mLSlide5

Specific Gravity

Ratio of a weight of substance to a weight of equal volume of standard

Usually water

Expressed without units

Specific Gravity =

Weight of substance

Weight of equal vol. waterSlide6

Specific Gravity Example

If 54.96

mL

of an oil weighs 52.78

g

, what is the specific gravity of that oil?

Specific Gravity =

52.78

g

oil

54.96

g

water

*why 54.96

g

of water? Because 54.96

mL

of water weighs 54.96

g

(specific gravity of 1)Slide7

Displacement (Plummet) Method

A body immersed in a liquid displaces an amount of the liquid equal to its own volume and suffers an apparent weight loss in weight equal to the weight of the displaced liquid

Weigh plummet in air

Weigh plummet in water

Weight plummet in oil

Weight of displaced oil = weight of plummet in air – weight of plummet in oil

Weight of displaced water = weight of plummet in air - weight of plummet in waterSlide8

Plummet Method Example

A glass plummet weighs 12.64

g

in air, 8.57

g

when immersed in water, and 9.12

g

when immersed in an oil. Calculate the specific gravity of the oil.

Specific gravity =

Weight of displaced oil

Weight of displaced water

=

12.64

g

– 9.12

g

12.64

g

– 8.57

g

= 0.865Slide9

Specific Volume

Ratio of the volume of a substance to an equal weight of another substance taken as a standard

Water Slide10

Specific Volume Example

If 25

g

of glycerin measures 20

mL

and the standard for comparison is (25

g

) water, what is the specific volume of glycerin?

Specific Volume =

20

mL

glycerin

25

mL

water

= 0.8Slide11

Practice ProblemsSlide12

Chapter 5 Page 73

What is the weight, in grams, of 3620

mL

of alcohol with a specific gravity of 0.820?Slide13

Chapter 5 Page 74

What is the volume, in pints, of 50 lbs of glycerin having a specific gravity of 1.25?Slide14

Chapter 5 Problem 2

A piece of copper metal weighs 53.6

g

and has a volume of 6

mL

. Calculate its density.Slide15

Chapter 5 Problem 6

If 380

g

of cottonseed oil measures 415

mL

, what is its specific gravity?Slide16

Chapter 5 Problem 15

If chloroform has a specific gravity of 1.476, what is its specific volume?Slide17

Chapter 5 Problem 18

What is the weight, in pounds, of 5 pints of nitric acid?Slide18

Chapter 5 Problem 27

If fifty glycerin suppositories are made from the following formula, how many milliliters of glycerin, having a specific gravity of 1.25, would be used in the preparation of 96 suppositories?

Glycerin 91

g

Sodium

stearate

9

g

Purified

water

5

gSlide19

Chapter 5 Problem 29

How many grams of dextrose are

contained

in a

250

mL

intravenous infusion of a dextrose injection containing 60

g

of dextrose per 100

mL

if its specific gravity is 1.20? Slide20

Chapter 5 Problem 24

Glycerin,

USP

(specific gravity 1.25) costs

$54.25 per pound. If students in a

dispensing

laboratory use 1 pint of glycerin in preparing compounded prescriptions, what is the cost of the glycerin used? Slide21

QuestionsSlide22

Reference

Ansel

, H. C. (2009)

Phamaceutical

Calculations

(13th Ed.).

Philadelphia:Lippincott

Williams & Wilkins, and

Wolters

Kluwer

Publishers