Correct spelling for the English word "elarson" is [ɪlˈɑːsən], [ɪlˈɑːsən], [ɪ_l_ˈɑː_s_ə_n] (IPA phonetic alphabet).
Trade name of strontium chlorarsenobehenolate, a white insoluble tasteless powder recommended in the treatment of anemia, chlorosis, chorea, and various diseases of the skin, in doses of gr. 1/8 (0.008) three or four times a day.
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.