Note 511 — Chapter XIII · THE ARSENIC GROUP. SULPHO-ACIDS AND SULPHO-SALTS
Reading edition
Neher (loc. cit.) suggested that the favorable action of the large excess of hydrochloric acid might well be due to the formation of AsCl5. McCay, J. Am. Chem. Soc., 24, 661 (1902), discusses the ionization of arsenic acid as a base, in connection with the precipitation of As2S5.