Reducing Formulae
You use the same method for reducing formulae.
Have a look at the example.
The source formula for Calamine Lotion is BP 1988:
You need to prepare 240 ml of Calamine Lotion. How much of each ingredient do you need?
Calamine
150g
Zinc Oxide
50g
Bentonite
30g
Sodium Citrate
5g
Liquefied Phenol
5ml
Glycerol
50ml
Purified water sufficient to produce
1000ml
You need to prepare 240 ml of Calamine Lotion. How much of each ingredient do you need?
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You have been given the source formula.
The total volume of the source formula is 1000 ml.
Decrease the formula by: Amount Required = 240 = 0.24
Total of Source Formula 1000
Total of Source Formula 1000
Multiply each ingredient by 0.24
| Calamine | 150 x 0.24g | = | 36.0g | Liquefied Phenol | 5 x 0.24ml | = | 1.2ml |
| Zinc Oxide | 50 x 0.24g | = | 12.0g | Glycerol | 50 x 0.24ml | = | 12.0ml |
| Bentonite | 30 x 0.24g | = | 7.2g | Purified Water | 1000 x 0.24ml | = | to 240ml |
| Sodium Citrate | 5 x 0.24g | = | 1.2g |
Check your calculations.
Checking the Calculations
Check the degree of the increase:
Check the degree of the increase:
| Calamine | 36.0/150 | = | 0.24 | Liquefied Phenol | 1.2/5 | = | 0.24 |
| Zinc Oxide | 12.0/50 | = | 0.24 | Glycerol | 12.0/50 | = | 0.24 |
| Bentonite | 7.2/30 | = | 0.24 | Purified Water | 240/1000 | = | 0.24 |
| Sodium Citrate | 1.2/5 | = | 0.24 |
Check the proportions of the chemicals:
| Source Formula | Calculated Amounts | |||||
| Calamine | 150/1000 | = | 0.15 | 36/240 | = | 0.15 |
| Zinc Oxide | 50/1000 | = | 0.05 | 12/240 | = | 0.05 |
| Bentonite | 30/1000 | = | 0.03 | 7.2/240 | = | 0.03 |
| Sodium Citrate | 5/1000 | = | 0.005 | 1.2/240 | = | 0.005 |
| Liquefied Phenol | 5/1000 | = | 0.005 | 1.2/240 | = | 0.005 |
| Glycerol | 50/1000 | = | 0.05 | 12/240 | = | 0.05 |
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