Calculating the Percentage Purity of Aspirin Tablets by Titrating with Sodium Hydroxide
Introduction
A titration was carried out to investigate the percentage purity of an aspirin tablet and compare that to the stated percentage on the box. A titration is the process of adding known amounts of reagent to a solution while monitoring the results. The reason a titration was used is because aspirin (acetylsalicylic acid), being an acid allows an acid-base titration to quantify the percentage of aspirin present. (Berg, 2012)
Aspirin is used to reduce fever and relieve mild to moderate pain from conditions such as muscle aches, toothaches, common cold, and headaches. It may also be used to reduce pain and swelling in conditions such as arthritis. Aspirin is known as a salicylate and a nonsteroidal anti-inflammatory drug (NSAID). (http://www.webmd.com/drugs/2/drug-1082-3/aspirin-oral/aspirin-oral/details, n.d.). Aspirin is also used as a blood thinner in small doses which is applied to treating cardiovascular conditions such as a heart attack.
Materials and Method
Risk assessment;
Before this experiment could safely be performed, a risk assessment had to be carried out. As this experiment required solvents, solutions and glassware. It was possible to identify the hazardous nature of these elements. First of these procedures was to ensure the stopper remained on the ethanol, and that the beaker of Sodium Hydroxide was in the middle of the bench to minimise the chance of spillage or getting knocked on the floor. It then made sure the glassware was either, safely secured or unable to fall off the bench.
Any hazards in the lab were then identified, and the risk assessed, see below. And it was ensured that the floor was adequately cleared, and put the lab coat and safety goggles were worn.
Risk Assessment
What is the hazard?
Who might be harmed and how?
What are you already doing?
Do you need to do anything else to control this risk?
Glassware
Students and staff
Glassware is checked regularly for cracks, chips and breaks.
Also Glassware is stored in a cupboard, with limited access.
The college employ a lab technician to reduce all risks.
Slips and trips
Students and staff
General good housekeeping is carried out. All areas are well lit. No hanging leads or cables. Students and staff keep work area clean e.g. chairs and bags under desks.
The college employ a lab technician to reduce all risks.
Chemicals
1. NaOH
2. Phenolphthalein indicator
3. Aspirin
4. 95% Ethanol
Students and staff
All chemicals are appropriately labelled. Caution labels can be clearly seen on bottles.
The college employ a lab technician to reduce all risks.
COSHH Assessment
What is the chemical that can cause harm
Who might be harmed
What are you already doing to control this risk
Do you need to do anything else to control this risk
Level of Risk
95% Ethanol (flammable)
Students and staff No naked flames around the chemical.
Stored in a controlled environment.
Flammable sticker on the bottle.
The college employ a lab technician to reduce all risks.
Low risk
Aspirin (digestion)
Students and staff
Ensure that there are none left around unsupervised.
The college employ a lab technician to reduce all risks.
Low risk
Phenolphthalein indicator (flammable)
Students and staff
No naked flames surround the chemical.
Stored in a controlled environment
Flammable sticker on the bottle.
The college employ a lab technician to reduce all risks.
Low risk
NaOH (0.1M)
Students and staff
Low dilution.
Kept in technician store away from pupils and untrained staff.
The college employ a lab technician to reduce all risks.
Low risk
Apparatus;
The apparatus used in this experiment are listed below;
Conical Flask
50ml Burette
500ml Beakers
Spatula
White Tile
Stand
10ml Pipette
25ml Pipette
Pestle & Mortar
Balance
Solvents used are below;
Sodium Hydroxide NaOH
95% Ethanol
Deionised Water
Phenolphthalein
