Solubility, Complexation, and Buffers in Pharmaceutical Science
Solubility Expression
Solubility is defined as the concentration of a solute in a solvent when the solution becomes saturated at a specific temperature and pressure. It is expressed as:
- Molarity (M): Moles of solute per liter of solution (mol/L).
- Molality (m): Moles of solute per kilogram of solvent (mol/kg).
- Parts per million (ppm): Milligrams of solute per liter of solution, often used for very low solubility levels.
- Percentage concentration: Expressed as weight/volume (% w/v) or weight/weight (% w/
History of the Periodic Table and Atomic Properties
How to Identify Elements
In 1830, John Jacob Berzelius, a Swedish chemist (1779-1848), proposed a method to represent the elements: using the first letter in Latin or, if two or more elements had the same initial, the initial letter followed by another present in the Latin name. For example, N for nitrogen, Na for sodium, and Ni for nickel.
Early Grouping of Elements
Many studies early this century established that the elements could be grouped into families with similar chemical properties, such as
Read MoreOptimizing Radiographic Processing: Techniques & Maintenance
Extended Processing in Mammography
- Extended Processing – Particularly useful in mammography
- 3 minutes (standard time is 90 seconds)
- Developer immersion time – doubled, but it is not necessary to alter developer temperature
- Significant disadvantage: longer dry-to-drop time.
- 2 principal advantages of EXTENDED PROCESSING: Greater image contrast & low patient dose
- Contrast increased by approximately 15%
- Image receptor sensitivity increased by at least 30%
- Thus, patient dose is reduced by at least 30%
- Improvements
Aromatic Compounds, Phenols, and Cycloalkanes: Properties and Uses
Hückel’s Rule
Definition: Hückel’s Rule determines whether a cyclic compound is aromatic. A compound is aromatic if:
- It is cyclic and planar.
- It is fully conjugated (alternating single and double bonds).
- It contains (4n+2)π electrons, where n is a non-negative integer (0, 1, 2…).
Example:
- Benzene (n = 1, 6π electrons): Aromatic.
- Cyclobutadiene (n = 1, 4π electrons): Anti-aromatic (unstable).
Importance: Aromatic compounds are more stable due to delocalized π electrons.
Structure and Uses of DDT,
Read MoreClassification and Properties of Non-Ferrous Metals
Classification of Non-Ferrous Metals
Non-ferrous metals are essential and are increasingly used in industry to manufacture many products. They are classified as follows:
- Heavy: Density greater than 5 kg/dm3. Examples include tin, copper, zinc, and lead.
- Light: Density between 2 and 5 kg/dm3. Examples include aluminum and titanium.
- Ultralight: Density less than 2 kg/dm3. Examples include magnesium and beryllium.
Non-ferrous metals are generally soft and have low mechanical strength. Therefore, they are
Read MoreAtomic Theory: From Ancient Greece to Modern Physics
First Discussions on the Subject
It was the Greek philosophers who began to question rationally, trying to find explanations or principles to explain the nature of things. For example, Thales of Miletus, who lived between the 5th and 6th centuries BC, postulated that the fundamental substance of the universe was water, from which it was possible to explain the constitution of all things.
A different view was that of Empedocles (5th century BC), who, by adding different traditions, argued that there
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