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in this section are available ready-made from Flinn Scientific to save valuable laboratory prep time.
The section is divided into several parts for your convenience.  Basic concepts of preparing solutions
 Preparation of simple inorganic salt solutions
 Preparations of acid and base solutions
 Recipes for Biological, Histological, and Chemical solutions
Laboratory Solution Preparation
• Basic concepts of preparing solutions
• Over 300 recipes of common laboratory solutions
• Solution preparation tips
Many of the reagents used in science are in the form of solutions which need to be purchased or prepared. For many purposes, the exact value of concentration is not critical; in other cases, the concentration of the solution and its method of preparation must be as accurate as possible. The Flinn Laboratory Solution Preparation reference section is designed for both the novice and experienced solution maker. It provides valuable information on the basic concepts of preparing solu- tions and instructions for preparing most solutions required in the high school science laboratory. Professional quality solutions are possible when high quality and fresh chemicals and solvents are used, and meticulous procedures are followed. Many of the solutions described
Basic Concepts of Preparing Solutions
BASIC CONCEPTS OF PREPARING SOLUTIONS continued on next page.
Molarity
The most common unit of solution concentration is molarity (M). The molarity of a solution is defined as the number of moles of solute per one liter of solution. Note that the unit of volume for molarity is liters, not milliliters or some other unit. Also note that one liter of solution contains both the solute and the solvent. Molarity, therefore, is a ratio between moles of solute and liters of solution. To prepare laboratory solutions, usually a given volume and molarity are required. To determine molarity, the formula weight or molar mass of the solute is needed. The following exam- ples illustrate the calculations for preparing solutions.
If starting with a solid, use the following procedure:
• Determine the mass in grams of one mole of solute, the molar
mass, MMs.
• Decide volume of solution required, in liters, V.
• Decide molarity of solution required, M.
• Calculate grams of solute (gs) required using equation 1. eq. 1. gs = MMs x M x V
• Example: Prepare 800 mL of 2 M sodium chloride. (MMNaCl = 58.45 g/mol)
gNaCl = 58.45 g/mol x 2 mol/L x 0.8 L gNaCl = 93.52 g NaCl
Dissolve 93.52 g of NaCl in about 400 mL of distilled water, then add more water until final volume is 800 mL.
If starting with a solution or liquid reagent:
• When diluting more concentrated solutions, decide what volume (V2) and molarity (M2) the final solution should be. Volume can be expressed in liters or milliliters.
• Determine molarity (M1) of starting, more concentrated solu- tion.
• Calculate volume of starting solution (V1) required using equa- tion 2. Note: V1 must be in the same units as V2.
eq. 2. M1V1 = M2V2
• Example: Prepare 100 mL of 1.0 M hydrochloric acid from concentrated (12.1 M) hydrochloric acid.
M1V1 = M2V2
(12.1 M)(V1) = (1.0 M)(100 mL) V1 = 8.26 mL conc. HCl
Add 8.26 mL of concentrated HCl to about 50 mL of distilled water, stir, then add water up to 100 mL.
Definitions
Buffer: A solution which tends to maintain a constant pH when excess acid or base is added.
Concentrated: For some commonly used acids and bases, the maximum solubility (at room temperature) in an aqueous solution or as a pure liquid.
Concentration: The relative amount of solute and solvent in a solution.
Hydrates: Compounds containing water chemically combined in a definite ratio. Computations using formula weight must take the water molecules into account.
Miscible: The ability of two liquids to be completely soluble in one another.
Molality: A concentration unit (m); defined as the number of moles of solute divided by the number of kilograms of solvent.
Molar Mass: The mass of a mole of any element or compound.
Molarity: A concentration unit (M); defined as the number of moles of solute divided by liters of solution.