Physical Pharmacy LAB PDF - Specific Gravity Determination

CYCLE SEM Physical Pharmacy LAB PHARM3A | TUTOR 1 1 MODULE 1: SPECIFIC GRAVITY DETERMINAT...

CYCLE SEM Physical Pharmacy LAB PHARM3A | TUTOR 1 1 MODULE 1: SPECIFIC GRAVITY DETERMINATION OF LIQUIDS PRE LABORATORY DISCUSSION step, which in conjunction with the determination of the boiling or congealing SPECIFIC GRAVITY DENSITY points and other physical attributes, comprised ratio of mass of a mass of substance per in the term character, discloses the identity, substance to mass of unit volume purity or otherwise of the substance. equal volume of another substance taken as STD Temperature '! * A very important variable in specific gravity !". $ = )= '( + determination. unitless has unit (g/mL) The common practice with regards to the numerically equal in the same in metric and determination of sp.gr. defined by the USP: metric and English English system (62.4 o "Unless otherwise stated, the sp. gr. system lb/ft3) basis is 25 deg./25 deg., i. e., the ratio varied value (1 for of the weight of a substance in air at water) 25deg. to that of the equal volume of apparent specific gravity apparent density water at the same temperature. true/absolute specific absolute density o 25 ̊/25 ̊ gravity relative density Specific Gravity Bottle (Pycnometer) Specific Gravity Special glass bottle used to determine sp. gr. Specific Gravity (Relative density / Specific weight) of liquids by weighing of the defined volume unitless expression of the ratio of the mass of Fitted glass stopper with a capillary tube a substance (Ws) to the mass of an equal through it, so that air bubbles and excess volume of another substance taken as fluids may escape from the apparatus. standard (Ww) Enables a liquid's density to be measured accurately by reference for an appropriate fluid, !"#$%&%$ ()*+%,- = !"#$%& () *+,*&-./" such as water, using an analytical balance !"#$%& () "0+-1 2(1+3" () !-&"4 5* Available in volumes ranging from 1mL to !". ( = 5! 50mL Ratio of one density to another density How to get specific gravity using pycnometer It tells us whether the sample will float or sink Step 1. Measure the weight of a clean, dry and in water empty pycnometer. Plays an important role in determining the Step 2. Weigh pycnometer filled with distilled performance of materials (flow properties) in water. dosage forms. Step 3. Weigh pycnometer filled with the sample Monitoring the relative density of solid liquid pharmaceutical materials can be useful during Step 4. Get the weight of the water/sample liquid the design optimization and scale up of - Weight of Pycnometer with (distilled manufacturing process for solid dosage forms water) or (sample liquid) - Weight of and may help achieve robust drug product empty pycnometer manufacturing process. Step 5. Solve for the Specific Gravity of the Specific gravity is always given first in defining substance: !"#$%& () *-361" the character of chemical liquids in the !"#$%&%$ ()*+%,- = !"#$%& () !-&"4 descriptive text of the USP While not always of itself sufficient to prove the identity, etc., It is always first and essential AD | PHARMACY 2A | 2021 1  MODULE 1: SPECIFIC GRAVITY DETERMINATION OF LIQUIDS Mohr Westphal Balance POST LAB DISCUSSION The scale relies on Archimedes Principle of buoyancy STANDARD SPECIFIC SAMPLE LIQUIDS Operates by suspending a glass tube into a GRAVITY sample of a solution of unknown density via a CLOVE OIL 1.038 – 1.060 thin platinum wire For lighter liquids, the plummet will sink while ETHYL ALCOHOL NMT 0.816 for the heavier liquids, it will float LIQUID Can quickly provide very close approximation 0.860 – 0.905 PETROLATUM of the specific gravity of any liquid Incapable of highly accurate readings, as large GLYCERIN NLT 1.249 temperature ranges in laboratories can affect SYRUP 1.313 its ability to duplicate results and the alignment of its pointers is based on human sight and If experimental sp gr is less than std sp gr it means it therefore full of potential for human error. has impurities or is less than the standard. Hydrometer Instrument used to measure the density of a liquid as compared to that of water. Usually consist of a calibrated glass tube ending in a weighted glass sphere that makes the tube stand up right when placed in a liquid. The greater the density, the tighter or closer the molecules are packed inside the substance, therefore the greater the density/specific gravity of a liquid the higher a hydrometer will be buoyed by it. Types of Hydrometer A. Baume hydrometers – calibrated to measure specific gravity of evenly spaced scales 1. Baume heavy hydrometer – for liquids heavier than water 145 !" $, = 145 − °23 2. Baume light hydrometer – for liquids lighter than water 140 !" $, = 130 + °23 B. Brix (BX) hydrometer – for determining the percentage by weight of sucrose AD | PHARMACY 2A | 2021 2