CLEANING KAURI GUM.

New Zealand Herald, Volume LIV, Issue 16696, 14 November 1917, Page 6

CLEANING KAURI GUM.

. SCIENTIST'S DISCOVERY. I SEPARATION IN SOLUTION. i [BT TELEGRAPH— CORRESPONDENT,] WELLINGTON. Tuesday. A method of cleaning kauri gum that is found in small pieces has been discovered by Dr. MacLaurin, the Government i analyst. The first part of the operation is j to immerse the gum, mixed as it is with ' dirt, in a strong solution of common salt. : Apparently the salt has no other part in j the process than to increase the specific gravity of the liquid, and so increase its floating power. The idea of the operation i is that the gum will float in the solution, j and that the dirt will sink. What actually happens when the gum is immersed j is that the whole mixture, except a small I portion of the heaviest of the dirt, floats. I The dirt is really of higher specific gravity ! than the solution, and it ought therefore jto sink. It floats because it is porous, and is full of tiny bubbles, and experiment has shown that even if left to stand ' for a long time the bubbles do not wholly disappear, and the dirt remains mixed with the gum. The problem of getting rid of the air is solved by seaiing up the mixture in an airtight cylinder or other vessel, and with an air pump creating a vacuum. By this means the air is extracted from the dirt and the dirt sinks, leaying the gum floating clean on the top of the solution*-. To remove the clean gum is then a simple ' operation. Even the solution need not be lost. The dirt may be filtered out of it and the brine used over again. The process is likely to prove one of great value to the gum industry. . '/