----------------+----------------+----------------- Gum or Dextrin. | Solution used. | [alpha]_{D} ----------------+----------------+----------------- | Per Cent. | Aden, 1 | 5 | - 33.8 Cape, 2 | 5 | + 28.6 Indian, 3 | 5 | + 66.2 Eastern, 4 | 5 | - 26.0 Eastern, 5 | 5 | - 30.6 Senegal, 6 | 5 | - 17.6 Senegal, 7 | 5 | - 18.4 Senegal, 8 | 2½ | - 19.6 Senegal, 9 | 5 | - 38.2 Senegal, 10 | 5 | - 25.8 Amrad | 2½ | + 57.6 Australian, 1 | 5 | - 28.2 Australian, 2 | 5 | - 26.4 Brazilian, 1 | 2½ | - 36.8 Brazilian, 2 | 2½ | + 21.0 Dextrin, 1 | 5 | +148.0 Dextrin, 2 | 5 | +133.2 Ghatti, 1 | 5 | - 39.2 Ghatti, 2 | 5 | - 80.4 ----------------+----------------+----------------- These numbers do not show any marked connection between the viscosity, etc., of a gum and its specific rotatory power. When gum arabic solution is treated with alcohol the gum is precipitated entirely if a large excess of spirit be used. With a view to seeing if the precipitate yielded by the partial precipitation of a gum solution was identical in properties to the original gum, we examined several such precipitates from various gums to ascertain their rotatory power. We found in each case that the specific rotatory power of the alcohol precipitate redissolved in water was not the same as that of the original gum. In other words these gums contained at least two bodies of different rotatory powers, of which one is more soluble in alcohol than the other. O'Sullivan obtained similar results with pure arabin. The experiments were conducted in the following manner: