‘Antacid’ is a common term used to describe substances, mainly bases, that are used to counteract excess stomach acid and relieve heartburn. In this lab report I am going to investigate the neutralising behaviour of six different antacids on hydrochloric acid. Antacids are available in a variety of different formulations and are mainly available as over-the-counter (OTC) preparations. Antacids work by neutralising excess stomach acid and by doing so they raise the pH of the stomach. The pain felt by the sufferer is commonly caused by peptic ulcers.
The gastrointestinal mucosa houses nerves. When these nerves are exposed (for example those in ulcers) and hydrochloric acid reaches them, the nerves signal pain to the central nervous system. The effect of aluminium ions can also contribute to indigestion. The ions can inhibit the smooth muscle cells and delay the emptying of the stomach causing. This is turn means that there is a build up in stomach acid.
In this lab report I am going to investigate the neutralising behaviour of six different antacids on hydrochloric acid. Antacids are available in a variety of different formulations The pH range of the stomach falls in the range between 1 and 4, depending on food intake and digestion. Usually the stomach has a pH that falls in between 1.5 and 2.5. This level can drop to 0.8 or even 0.4 in some cases when the stomach is not emptied. This build up in acid can also cause acid reflux up the oesophagus. This occurs when the lower oesophageal sphincter is abnormally relaxed, causing it to remain open. This leaves an open passage way for acid from the stomach to reflux up the oesophagus. This commonly causes heart burn.
The hydrochloric acid, that causes these conditions, is produced in the stomach by parietal cells. These cells are located in the gastric gland. These cells produce hydrochloric acid by the following equations: CO2 + H2O H2CO3 HCO3 + H+ At this point HCO ions are pumped out of the cell and at the same time ions is being pumped in. This is known as counter-transport. The H+ and Cl� are then moved out of the parietal cells into the lumen of the gastric gland. The Cl� is moved by facilitated diffusion and the H+ is pumped out by active transport. The ions are then secreted into the stomach by the gastric gland.
When the gastric gland produces too much acid, antacids are required to bring up the pH in the stomach. There are many different types of antacids available. The most common types of antacids that can be found are: aluminium and magnesium-containing, sodium bicarbonate, bismuth-containing, alginates and simeticone. Antacids have very few interactions. However they should preferably not be taken at the same time as any other drugs and it may affect absorption. In general the side effects from antacids are mainly constipation or diarrhoea. These can be prevented by the pairing of ingredients. Another more common side effect is flatulence; this is mainly due to the liberating of carbon dioxide.
Materials pH buffer (pH 4), unknown antacids 1, 2, 3, 4, 5 and 6, hydrochloric acid (0.05M), pestle and mortar, pH meter, beakers (50ml and 500ml), magnetic stirrer, stopwatch, deionised water, measuring cylinders (50ml and 500ml). Method The pH meter was set up using a clamp and stand, so that it rested above the magnetic platform. The pH metre was able to be lowered in and out of the beaker to take readings.
The pH meter was standardised using a pH buffer (pH 4). The buffer was poured into a 50ml beaker and was placed on the platform. The pH meter was placed into the solution. The meter was altered until the meter read ‘pH 4’. The solution was then tipped back into its container and the beaker was washed and discarded of. A table was constructed and labelled ready for readings to be recorded. 200ml of hydrochloric acid (0.05M) was measured using a 500ml measuring cylinder and was transferred into a 500ml glass beaker. The beaker was placed on the magnetic platform and the magnetic stirrer was allowed to stir the acid solution for 2 minutes, at a medium speed. A reading of the initial pH was read and recorded in the table. At this time the stopwatch was set for 30 minutes.
The recommended amount of antacid 1 was crushed in a pestle and mortar. The crushed antacid was then mixed in 25ml of deionised water. The mixture was added to the beaker containing the hydrochloric acid and the stopwatch was started. Readings of the pH were taken at 1, 2, 5, 10, 15, 20, 25 and 30 minutes and recorded in the table. The following steps were repeated for unknown antacids 2 and 3. For antacids 4, 5 and 6 no addition of deionised water was required as the antacids were already in liquid form. Therefore the recommended doses of antacids 4, 5 and 6 were measured in a 50ml measuring cylinder and added straight to the hydrochloric acid. The experiment was carried out as outlined before.