Dilutions and concentrations Lab 6, Summaries of Pharmacy

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Dilutions and

concentrations

Lab 6

Dilution and Concentration

• Dilution means when a given solution of a

mixture of high concentration is diluted by

addition of the suitable diluents or admixture

with solution of lower concentration.

• While concentration means when a given

solution of a mixture of low concentration are

concentrated either by addition of active

ingredient or by admixture with higher strength

solution or by evaporation of the diluents.

• We have different types of dilution either of

liquids or solids.

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Dilution Law

• C

1

V

1

= C

2

V

2

• The concentration is expressed either by

normality, molarity or percent (%).

• Normality is an expression of the concentration

of the solution in terms of equivalent per liter of

solution (number of gram eq.wt per 1000 ml).

• Morality is the concentration of the solution in

terms of moles per liter.

Dilution of alcohol

• When alcohol is diluted with water a noticeable contraction in volume occurs so it is difficult to calculate the amount of water to be add because alcohol interaction with water by bounding (H- bond) and lead to contraction but this contraction of volume not affect the weight of alcohol and water added.
• Examples Rx Boric acid 10 gm Alcohol 70 % 30 ml Alcohol available 90 %
• How many mls of 20 % alcohol can be used to prepare 25 ml of 10 % alcohol? C 1 V 1 =C 2 V 2 20 % x V 1 = 10 % x 25 ml V 1 =12.5ml of 20 % alcohol and complete the volume to 25 ml.

Problems

• If 500 ml of 15 % v/v solution are diluted to 1500 ml.

What will be the percentage strength?

C 1 V 1 = C 2 V 2

15 % x 500 ml =C 2 x 1500 ml

C 2 = 5 %

• How many mls of a 1:5000 (w/v) solution of potassium

permanganate can be made from 50 ml of a 5 % solution?

C 1 V 1 =C 2 V 2

50 ml x 5 % = 0.02% x V 2

V 2 = 1250 ml

Reducing and Enlarging Formula

• Pharmacist may have to reduce or enlarge the

formula in pharmaceutical preparation. In

large manufacturing the official formula must

be enlarged, while in the pharmacy or on

small products the official formula must be

reduced

• Factor= desired amount/ specified amount Examples: Rx Codeine phosphate gr V Amaranth solution ɱ XV Alcohol 10 % fƷ ss D.W. q.s f ℥ **l

1. Mitt f** ℥ **II
2. Mitt f** ℥ ss Calculation( 1 ): 5 / 15 = 0.3 g of codeine phosphate 15 / 15 = 1 ml of amaranth fƷ ss= 2 ml f℥ = 30 ml f Ʒ II= 60 ml factor= 60 / 30 = 2 0.3× 2 = 0.6 g of codeine phosphate 1 × 2 = 2 ml of amaranth 2 × 2 = 4 ml of alcohol 60 × 3 / 4 = 45 ml 45 - ( 4 + 2 )= 39 ml

Calculation

• f℥ ss= 15 ml factor= 15 / 30 = 0.
• 0.3 × 0.5= 0.15 g of codeine phosphate
• 1 ×0.5= 0.5 ml of amaranth
• 2 ×0.5= 1 ml of alcohol
• 30 ×0.5= 15 ml
• 15 × 3 / 4 =11.25 ml
• 11.25-(0.5+ 1 )=9.75ml
• Procedure Follow the same of the above procedure.

Home works

• Rx Calamine 80 g

Zinc oxide 80 g

Glycerin 20 ml

Bentonite magma 250 ml

Calcium hydroxide qs 1000 ml

Mitt gallon

Rx Atropine sulfate gr XX

Camphor water ɱ XV

D.W qs fƷ I

Mitt fƷ V