RELATIONS BETWEEN ROTATORY POWER AND STRUCTURE IN THE SUGAR GROUP. V.<sup>1</sup> THE CHLORO- AND BROMO-ACETYL DERIVATIVES OF ARABINOSE. THE NOMENCLATURE OF ALPHA AND BETA FORMS IN THE SUGAR GROUP. SOME DERIVATIVES OF 1,6-BROMO-ACETYL GLUCOSE, GENTIOBIOSE AND MALTOSE<sup>2</sup>