Phthalylsulfathiazole shows up in the world of antibiotics as a classic sulfa compound, famous among those who have dug through pharmacology textbooks. People tend to rely on it in gastrointestinal infections, largely because the chemical structure stays stable in the gut and gets broken down slowly, striking that balance between potency and safety within the digestive system. This material takes the form of a pale yellowish solid, with molecular formula C17H13N3O5S2 and a molar mass of about 419 g/mol. In every container of this substance, what you often see is a blocky, crystalline powder that doesn’t exactly dissolve in water but does spread nicely in the typical lab solvents.
On paper, the structure of phthalylsulfathiazole stands out with its benzene ring hugging a sulfonamide group, tied to a thiazole ring by a classic sulfa bridge. This arrangement drives both its biological impact and its interactions during synthesis. Producers use phthalic anhydride and sulfathiazole as key raw materials, guiding the reaction under careful conditions to minimize side products. The density lands near 1.5 g/cm³ and keeps the product workable through milling or compaction into flakes or powder. This bulk density and flow matter a lot when mixing with excipients for tablets or fine-tuning the material’s packing into capsules.
Sitting at room temperature, phthalylsulfathiazole keeps solid form, usually as fine powder or flakes with a faint yellow tint—never pearl or liquid, and certainly never cloudy solution. Particle size directly influences how the powder handles moisture. Because it resists dissolving in water, you’ll need organic solvents like ethanol to pull it into solution, and that’s only partial. In my own experience in research labs, bottles of this stuff keep well sealed, since the powder picks up moisture from humid air. Avoiding clumping or caking takes extra effort, especially during summer months where lab humidity can spike. The material’s density and granule shape make it easy to pour, but it’ll dust the air if handled carelessly—use a fume hood or at least a dust mask when weighing or mixing the substance.
Phthalylsulfathiazole doesn’t scream danger like some industrial acids or bases, but safety data sheets label it as hazardous on ingestion in large doses and potentially harmful upon direct contact with eyes and skin. Chronic exposure may trigger allergic reactions, especially among people with sulfa allergies, and its environmental impact is not trivial—the compound does not break down rapidly in soil or water. In standard classrooms, safe handling means gloves, goggles, and closed containers after each use. Dumping leftover raw material without neutralizing it can pose risks to both user and ecosystem. Years spent working in university prep rooms drilled into me the habit of always reviewing the HS Code associated with such chemicals, in this case 2935009090, which facilitates safe tracking, transport, and disposal.
As an active ingredient in older antibiotics, phthalylsulfathiazole saw its heyday in the twentieth century before modern agents replaced it for many uses. This doesn’t mean pharmacies have abandoned it completely—some countries still include it in infection protocols where resistance hasn’t run rampant. Distributors typically ship the material in sealed drums marked by net weight, batch number, purity (over 99% for pharmaceutical grade), and strict storage requirements: cool, dry, and dark to keep the chemical bonds from breaking down too soon. I’ve seen expired product clump and discolor, losing reliability for analytical or medicinal use. Regulation on this compound arises from both its pharmacological activity and its status as a raw chemical, so authorities monitor inventory and waste quite closely.
The key to responsible use of phthalylsulfathiazole weighs most heavily on proper disposal and clear hazard communication, especially for raw material handlers. Where possible, facilities should stick with dedicated waste streams—soluble residues funneled into chemical waste, spent powder handled as hazardous solid rather than simply dumped. Training staff to recognize allergic symptoms and respond to spills helps limit accidental exposure, especially given how fine powders can become airborne in a busy work environment. Researchers and manufacturers can also switch to smaller packaging, reducing how much product sits open at a time, and limit exposure during transfer by automating as many steps as practical.
Chemical Name: Phthalylsulfathiazole
Molecular Formula: C17H13N3O5S2
Molecular Weight: 419.44 g/mol
Physical State: Yellowish solid, crystalline or powder
Density: ~1.5 g/cm³
Melting Point: 200-212°C (decomposes)
Solubility: Almost insoluble in water, partly soluble in ethanol
HS Code: 2935009090
Hazard Class: Harmful if swallowed, irritant, possible allergen
Raw Materials: Phthalic anhydride, sulfathiazole
Typical Packaging: Drum, sealed container, labeled with batch data and hazard info
