Direct Measurements of the Osmotic Pressure of Solutions of Certain Colloids.

amounts to I 74 per cent. of inorganic constituent. The long duration of dialysis in a charmber specially built for rapid equalization, and the difference in percentages of ash on the two sides, at the end, viz., 0-032 and 0-170 per cent. show that this inorganic matter is not to be regarded as an impurity in the gelatine, but qs an intrinsic! part in combination or adsorption with it. Analyses of the two fluids at the end showed o-oo6 per cent. of total solids on the water side, and 6-25 per cent. of total solids on the solution side of which 6-og per cent. was organic, and o-i6 per cent. was inorganic ash. In two other experiments similar results were obtained, a 6 per cent. solution giving an osmotic pressure of 142 mm. at 150 C., and a I0 per cent. solution an osmotic pressure of 276 at 130 C. This solution showed a small pressure of mm. of at 170 The pressure was raised artificially to 20 mm., slowly fell again. This shows that if gum tragacanth possesses an osmotic pressure at all in water it is scarcely measurable even by the direct method. Experiment II.-This experiment was on the effects of converting the serum proteids into alkali albumen by boiling with I per cent. caustic potash, and measuring osmotic pressure against saline (o075 per cent.) to which an equal amount of caustic potash had been added. The result showed an immense rise in osmotic pressure, similar to that obtained by Moore and Parker (oc. cit.). The experiments were carried out in December, I904, and are at a lower temperature than the preceding one.