 Dear students, most of the reagents used in the scientific laboratory are in the form of solutions that need to be prepared or purchased. For some cases, the exact concentration of the solution is not important, while for other cases, the concentration and the method of preparation of the solution needs to be as accurate as possible. Today, we will learn how to make solutions in the laboratory. But before that, we need to get acquainted with the glass we're used for this purpose. This is a glass pipette that is used to transfer fixed volumes of liquids from one container to another. The pipette that I am holding at the moment can measure up to 25 ml of the liquid. Remember that you should never use mouth pipetting for transferring liquids. Please use a pipette sucker, pipette filler or pipette bulb for transferring the liquid. Is a volumetric flask that can be used in the preparation of fixed volumes of solutions. These flasks can only measure up to a single volume. For instance, this flask can be used to prepare a solution of 500 ml only. This single mark here indicates that when volume of the solution reaches up to this mark, the volume will be 500 ml. These flasks are available in 100 ml, 250 ml, 500 ml and 1000 ml capacities. This is a measuring cylinder. Measuring cylinders can also be used for preparation of solutions and come in various sizes with different capacities. For instance, this is a 10 ml measuring cylinder, this is a 100 ml measuring cylinder and this is a 500 ml measuring cylinder. This is a conical flask and like other glassware, this also comes in varying sizes of different capacities. This is a beaker and is also available in different capacities. Remember that beakers and flasks may be used while preparing solutions that are never used to define the total volume or the final volume of the solution. Whenever preparing solutions, always raise the final volume in a narrow necked glassware such as a volumetric glass or a measuring cylinder. Also note that when preparing solutions, always use the upper meniscus for colored liquids and lower meniscus for colorless liquids to avoid parallax error. Concentration is a measure of the relative proportion of solute and solvent present in the solution and can be measured in terms of percentage, molarity, molality and normality. Now that we have learnt calculations, we will be preparing a 2% solution of sodium chloride. Whenever using reagents or salts in the laboratory, ensure that you read the expiry date on the bottle and read any warning or hazard instructions that are given on the label of the bottle. To make the solution, we will first weigh 2g of sodium chloride at approximately 30ml of distilled water. Total volume of 100ml, we can use any volume less than 50ml at this stage. Solution to dissolve all the salt. The salt has dissolved completely, transfer this to a measuring cylinder. Place the volume of this solution to 100ml using distilled water. Told earlier, read the lower meniscus for colorless liquids. Once the solution is ready, transfer it to a labelled bottle and store it. We will prepare filler sodium hydroxide solution. For this purpose, we will be using aluminium foil to weigh the sodium hydroxide. Pellets get hydrated very quickly, so this step needs to be done quickly. We will need to weigh 20ml of distilled water to this pellet. Solution to dissolve the pellet. You will notice that heat is liberated as sodium hydroxide dissolves in the solution. Large volumes of sodium hydroxide solution, you can do this step using a magnetic stirrer to avoid splashing. Once the pellet has dissolved completely, transfer this solution to a measuring cylinder and raise its volume to 50ml using distilled water. The solution has been made up to 50ml, transfer it to a labelled reagent bottle. Make dilute solutions from concentrated solution. To prepare 0.1 molar sodium hydroxide solution from 0.5 molar sodium hydroxide solution, we will first take 10ml of the stock solution, that is 0.5 molar sodium hydroxide solution. Trim of this solution to 50ml using distilled water to prepare 0.1 molar sodium hydroxide solution. Put this solution to a labelled reagent bottle, each of any solution using a pH meter. The bulb of the pH meter from its solution, immerse it in distilled water. Ensure that at any point during measurement, the bulb of the pH meter does not come in contact with the walls or base of the container. Then, wipe the bulb of the pH meter using a lint-free tissue paper. Pour the test solution in a beaker, first the bulb in this solution. Allow the reading on the pH meter to stabilize. Of this solution is 12.68. Once you have measured the pH, wash the glass bulb again in distilled water. pH meter is very sensitive and needs to be handled carefully. Once you have taken the reading, place the bulb in its solution again. This container contains a solution of potassium chloride, of normality. Normality is generally used for acids and bases. To calculate the normality of an acid, we will need information from its bottle. This is a bottle of sulfuric acid. Check the percentage purity of this sulfuric acid. The percentage purity mentioned on the bottle is 97%. Next, we need to check the specific gravity of this sulfuric acid. Specific gravity in simple terms is basically the density of this solution relative to water. A specific gravity greater than one indicates that this solution is heavier than water. The specific gravity mentioned on this bottle of sulfuric acid is 1.84. The portion about sulfuric acid has to come before the part about measuring pH.