Conversion of Weights 1. Convert 12.5 g to grains: 2. Convert 5 mg to grains: 3. Convert 6.2 gr to milligrams: Percentage Error Practice Problem The least weighable quantity is defined as the amount that can be weighed accurately within a certain permissible % error (usually 5%). smallest quantity (mg) = (100%) (balance sensitivity in mg) acceptable error (%) balance sensitivity in mg acceptable error as decimal 4. A pharmacist attempts to weigh 0.375 gram of a given substance on a balance of dubious accuracy. When checked on a highly accurate balance, the weight is found to be 0.400 gram. Calculate the percentage of error in the first weighing. 5. Using a graduated cylinder, a pharmacist measured 65 milliliters of a given liquid. Checking the measurement with a narrow-gauge burette, it is determined that the pharmacist had actually measured 71 milliliters. What is the percentage of error in the original volume measured?