PRELAB 7

ALLIGATION PROBLEMSLIQUID PARAFFIN EMULSION

ALLIGATIONP.45

ALLIGATION MEDIAL

Used to calculate the “Average Percentage Strength” of mixture of two or more substances whose quantities and concentrations are known.

nnCQCQCQQC ........2211

What is the percentage of alcohol in a lotion containing 1500ml. of witch hazel (14% alcohol), 2000ml. of glycerin, and 5000 ml. of 50% alcohol?

ALLIGATION ALTERNATE

Used to calculate the number of parts of two or more components of a given strength when that should be used to prepare a mixture of desired strength.

yb

c

xaPercent given

Percent desired

Parts required

a

b

c

x

yminus

gives

Number of parts ofminus

gives

Number of parts of

Example In what proportion should alcohols of 95% and

50% strengths be mixed to make 270 ml 70% alcohol?

95

50

70

25

20minus

gives

Number of parts ofminus

gives

Number of parts of

45:25:20

%70:%50:%95

270150120

Mix 120 ml of 95% alcohol with 150 ml of 50% alcohol to produce 270 ml of 70% alcohol.

In what proportion should 20% benzocaine ointment be mixed with ointment base to produce a 2.5% benzocaine ointment?

20%

zero%

2.5%

17.5

2.5

How many grams of zinc oxide should be added to 3400 g. of a 10% zinc oxide ointment to prepare a product containing 15% of zinc oxide?

100%

10%

15%

85

5

100% : 10%Parts 5 : 85grams x : 3400gx= 200 g

A hospital pharmacist wants to use three lots of ichthammol ointmentcontaining respectively 50%. 20%, and 5% of ichthammol. In whatproportion should they be mixed to prepare a 10% ichthammol ointment?

50%

20%

5%

10%

40

5

+ 10 = 50

5

50% : 20%: 5% 5 : 5 : 50

in what proportion may a pharmacist mix 20%, 15% ,5% , 3% zinc oxide ointment to produce 10% ointment

20%

15%

5%

3%

10%

10

5

5

7

20%

15%

5%

3%

10%

5

7

10

5OR

There are 5 types of problems1. Mixing of two different concentrations to produce

a third intermediate one (as the previous example)2. Dilution: mixing of a solution with concentration x

% with the free base where a=x% and b=0%3. Concentration: mixing of a solution with

concentration x% with the active ingredient where a=x% and b=100%

4. Mixing of 3 different concentrations.5. Mixing of 4 different concentrations.

LIQUID PARAFFIN EMULSION (P.95)

Rx

Liquid Paraffin ℥ss 15 mlGum Acacia Q.S.Spirit Mentha min xv (15 x 0.06 = 0.9 ml)Water to ℥ii 60 mlFiat: HaustusSig.: Statin

Keep in a Cool Place

Shake The Bottle

The Draught

To be taken at once.

Liquid Paraffin is a mineral oil

Prepared using the dry gum methodUses It softens fecal contents by retarding

water reabsorption, so it is useful in chronic constipation.

O W G

3 2 1

15 ml 10 ml 5 gm

15 ml Oil on oneside

Dry gum Method

In a dry mortar; add gum & grind with pestle

Place gum in a line in the center

Triturate with whipping motion until primary emulsion is formed (white , thick ,cracking sound)

Continue triturating for 2 min. (stabilization)

Trituration must be:1.From the wrist.2.In one direction.3.In all parts of the

morter.4.Continueous.5.Very Fast.

10 ml Water on the

otherside

In test tube put 10 ml water + 0.9 ml spirit

mentha Mix well

Add to emulsion portionwise with

stirring

10ml Water Dpwise &triturate

10ml Water portion-wise

& triturate

Transfer to a cup measure

Primary Emulsion

Wip with

a tissue

Adjust volume to 60 ml

+ 10 ml water

Wet gum Method

In a dry mortar; add gum & grind

with pestle

+ 15 ml Oil dropwise

& triturate

adjust volume to 60 ml with

water

Triturate with whipping motion until primary emulsion is formed (white , thick ,cracking sound)

Continue triturating for 2 min. (stabilization)

10ml Water dpwise

10ml Water portion-wise

Transfer to a cup measure

triturate until the gum is dissolved to form mucilage.

If a “ropy” appearance, stop the addition of oil , few drops of water should be added until the mixture becomes uniform.

Dry gum method

Wet gum method

Oil and water are added at once

Water is added to dissolve the gum then oil is added dropwise

If primary emulsion isn’t formed, can’t be corrected , therefore discard

If ropy appearance , stop oil addition and add few drops of water to maintain the emulsion

Difference Between Both Methods