Precautions
What is the main impurity in aspirin?
Abstract. Salicylic acid is a major hydrolytic degradation product of aspirin, responsible especially for gastric irritation during oral aspirin administration. This impurity was investigated in 12 different brands of aspirin formulation readily available in our locality.
How is aspirin separated from impurity?
Any remaining contaminants are removed by recrystallization in a solvent in which aspirin is sparingly soluble. Aspirin separates then as crystals leaving impurities behind in solution. This process should give a relatively clean product, whose purity can be determined by melting point analysis.
What makes aspirin pure?
The purity of acetylsalicylic acid was determined by melting point. In this experiment the melting range for acetylsalicylic acid is 144°C-172°C which is higher than commercial aspirin which is132. 8°C-138.9°C, meaning that acetylsalicylic acid obtained in this experiment contained impurities.
Which solvent is used in purification of aspirin?
The synthesis reaction of aspirin is shown below: Since acetic acid is very soluble in water, it is easily separated from the aspirin product. The aspirin isolated in this step is the “crude product”. A “purified product” can be obtained through recrystallization of the crude product in hot ethanol.
How do you test for impurities in aspirin?
The purity and amount of acetylsalicylic acid in aspirin can be measured using a Visual Spectrophotometer. Here's why: when iron is added to aspirin, it produces violet tetraaquosalicylatroiron complex. To put it simply there is a visible violet color reaction.
How do you increase the purity of aspirin?
Add hot, but not boiling, water until it dissolves. A mass of very pure Aspirin crystals will form; cool the flask by surrounding it with cold water”. Filter them again and rinse the crystals with the chilled water. ”The insoluble impurities remain on the filter paper and the filtrate contains the product.
What is the purity of commercial aspirin?
That being said, IF the stated assay values can be trusted, your commercial aspirin has undergone considerable decomposition (usually it's quite close to 100% pure when first made and tabletted). [You might wish to reference the US Pharmacopoeia for current purity requirements for aspirin tablets.]
Why is ethanol used to purify aspirin?
Ethanol has been chosen as the solvent because the polar nature of the hydroxyl group causes ethanol to dissolve many ionic compounds, moreover the ethanol molecule also has a non-polar end, and it will also dissolve non-polar substances. While cooling, crystallization takes place.
What happens when aspirin dissolves in water?
Aspirin is a pain reliever and fever reducer, but if it's allowed to react with water then it can undergo hydrolysis, forming salicylic acid and acetic acid, which is no longer effective. This reaction can occur under acidic or basic conditions.
What happens when ethanol is added to aspirin?
These results suggest that ethanol enhances aspirin absorption from the gastrointestinal tract but has no influence on its metabolism. Thus, it is dangerous to ingest the alcohol and aspirin at the same time, as this may exacerbate the acute toxicity of aspirin.
How does recrystallization remove these impurities?
Recrystallization is a technique used to purify solid compounds. Solids tend to be more soluble in hot liquids than in cold liquids. During recrystallization, an impure solid compound is dissolved in a hot liquid until the solution is saturated, and then the liquid is allowed to cool.
How do you separate aspirin and salicylic acid?
The purification can be done in two ways: by recrystallization in hot ethanol or in acetone or in a mixed solvent ethanol/water or by a process using distillation. The recrystallized acetylsalicylic acid and the solid impurities (unreacted salicylic acid) should remain dissolved in the solution.
How is acetic acid removed from aspirin?
Some of the other compounds, acetic anhydride and acetic acid, dissolve in water, but salicylic acid is only slightly soluble in cold water. Vacuum filtration will separate the crystalline aspirin away from everything else in the reaction mixture except for any salicylic acid that did not react.
Why is water used as a solvent in recrystallization of aspirin?
Because aspirin is less soluble in cold water. In fact, aspirin is not very soluble in water at all, which is why you are supposed to take it with lots of water. You are not "chilling the aspirin", you are preventing it from dissolving too much so that you have a better yield of your product.