In chitin extraction from black tiger shrimp shell waste, HCl is the commonly used decalcifying agent. However, it is considered a harsh chemical. An alternate was found by using organic acids. Conditions for deproteinization were: 1M NaOH at 95 degrees C for 6 h and solid-to-solvent ratio of 1:15 (w/v). Demineralization involved treatment with 0.25M HCl at ambient temperature for 30 min with agitation. The optimal solid-to-acid ratio was 1:30 (w/v) and this led to 86.5 +/- 1.2% purification of chitin. With the same conditions, the optimal ratio of mixed acids (0.25 M HCOOH and 0.25 M C6H8O7 at 1:2 (v/v)) was 1:28 (w/v) with chitin purification of 88.1 +/- 1.8%.