パラアミノサリチル酸とその塩の分解に関する物理化学的研究 (第6報)

パラアミノサリチル酸とその塩結晶の安定性

抄録

Following earlier reports on the reaction of p-aminosalicylic acid (PAS) and of its sodium salt (PAS-Na) in aqueous solution, decomposition of these and other salts was examined by mixing various buffer salts with PAS, PAS-Na, complex salt of calcium p-aminosalicylate (PAS-Ca₂), and calcium p-aminosalicylate (PAS-Ca), and maintaining these in a dessicator over saturated potassium nitrate solution or saturated ammonium chloride solution. The buffer salts used were ammonium dihydrogenphosphate, potassium dihydrogenphosphate, sodium oxalate, and borax. Results of these experiments were considered from the point of induction period (t′) and firstorder reaction period.
On addition of ammonium dihydrogenphosphate, PAS was the most stable and, since the acid was generally more stable in lower humidity, it was considered that water took part in this reaction. With the addition of potassium dihydrogenphosphate, the induction period of PAS salts was much shorter than that in the use of the ammonium salt, there being almost no induction period at 50° and 60°. However, there was a definite induction period in the case of PAS at all temperatures tested. With the addition of sodium oxalate, both PAS-Ca and PAS-Ca₂ showed two induction periods, t₁′ and t₂′, at 50°, and they were found to be far more labile than other PAS salts at 60°. On the other hand, addition of borax showed the first-order reaction constant, k, to be larger only in PAS-Na, the other three samples showing almost the same values.