The impact of four inorganic acids (hydrochloric, sulfuric, nitric and perchloric) and six organic acids (formic, acetic, citric, tartaric, oxalic and ascorbic) on the acid concentration in raw TATP crystals and the behavior of TATP during heating have been studied. The residual acid content in solid TATP depends on the type of acid and on its concentration in the reaction mixture. Increasing the concentration of acid in the reaction mixture leads to a higher acid content in TATP crystals. Sublimation of TATP during storage also has a significant impact on the acid concentration in TATP crystals. Sublimation of TATP gradually increases the content of non-volatile acid in TATP crystals (sulfuric and solid organic acids) while the content of volatile acids (hydrochloric, nitric) does not significantly change during TATP sublimation. The increasing sulfuric acid content in TATP crystals during sublimation decreases thermal stability of TATP and the start of TATP decomposition was observed even at 45 degrees C. The concentration of volatile hydrochloric and nitric acids does not change significantly in TATP crystals during sublimation and, therefore, the sublimation process does not have an impact on TATP's thermal stability in these cases.