Students commonly find specialist scientific language problematic. This study investigated developments in chemical language usage by six "non-traditional" students over the course of 1 to 4 years. The students participated in semi-structured interviews and were asked to explain specific chemical scenarios. Interviews were transcribed and analysed for the correct use of macroscopic and sub-microscopic scientific language and occurrences of interlanguage. Results indicate that students experienced difficulties incorporating sub-microscopic language into their explanations. Students also demonstrated "potential" chemical interlanguage, which we characterise as transitioning from vague to defined use, combining everyday and scientific language, interchanging terms and omission of terms and formulaic phrases. Implications of these findings are discussed in relation to science pedagogy.