Ratio SolutionsRatio solutions are usually prepared in strengths asfollows: 1:10, 1:150, 1:1000, 1:25000, etc., using evennumbers to simplify the calculations. When a solutionis made by this method, the first term of the ratioexpresses the part of the solute (the substancedissolved in a solvent), while the second termexpresses the total amount of the finished product.Rules for solving ratio-solution problems are asfollows:W/W (weight/weight) solution: Divide the totalweight (grams) of solution desired by the largernumber of the ratio, and the quotient will be thenumber of grams of the solute to be used.W/V (weight/volume) solution: Divide the totalvolume (in milliliters) of solution desired by the largernumber of the ratio, and the quotient will be thenumber of grams of the solute needed.V/V (volume/volume) Solution: Divide the totalvolume (in milliliters) of the solution desired by thelarger number of the ratio, and the quotient will be thenumber of milliliters of the drug to be used.Percentage solutions from stock and/or ratiosolutions:PHARMACEUTICAL PREPARATIONSLEARNING OBJECTIVE:Recall thecomposition and physical characteristics ofcommonly used pharmaceutical prepara-tions.While assigned to a pharmacy or naval vessel, youmay be required to make pharmaceutical preparations.The following sections will acquaint you with thecomposition and physical characteristics of some ofthese preparations.ElixirsElixirs are aromatic, sweetened hydroalcoholicsolutions containing medicinal substances. The colorof elixirs varies according to the nature of theingredients; some are artificially colored.SuspensionsSuspensions are coarse dispersions comprised offinely divided insoluble material suspended in a liquidmedium. To keep the insoluble material suspended, athird agent, called a suspending agent, is required. Theprocess of mixing or combining the ingredients to forma suspension is called reconstitution.OintmentsOintments are semisolid, fatty, or oily preparationsof medicinal substances. These preparations are ofsuch a consistency as to be easily applied to the skinand gradually liquefy or melt at body temperature.Ointments vary in color according to their ingredients.The base of an ointment is generally greasy in texture,6-16Example: How many grams of KMNO_{4}are neededto make 500 g of a 1:2000 solution?Solution:500 ÷ 2000 =0.25 g of drug needed500 - 0.25 = 499.75 g of solvent needed500.00 g total solutionExample: How many grams of bichloride of mercuryare needed to prepare 500 ml of a 1:1000 solution?Solution:500 ÷ 1000 =0.50 g of drug neededAdd sufficient solvent to make 500 ml of solution.Example: From a 1:10 solution of silver nitrate inwater, prepare 60 ml of a 1.5% solution of the sameingredients.Solution: A 1:10 (W/V) solution contains 1 g ofsolute and enough solvent to total 10 ml of solution(finished product). Therefore, 1 ml of the solutionwould contain 0.1 g of the solute. Since it is re-quired that 0.9 g of the solute be used to prepare60 ml of the required strength, use 9 ml of the stocksolution and enough solvent (water) to make the totalvolume measure 60 ml.Example: How many milliliters of HCl are needed toprepare a 1:250 solution with a total volume of 500ml?Solution:500 ÷ 250 =2.0 ml of drug needed

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