Grain futures prices closed mixed on the Chicago Board of Trade Thursday. Corn was off 3 1/4 to off 8 3/4, soybeans were up 1 3/4 to up 8, wheat was off 1 to off 6 3/4 and oats were off 8 to off 10. Corn prices slipped on light trading that turned into late profit taking. Wheat prices fell modestly with export sales that were less than expected at 279,300 metric tons for the week. Soybeans gained from news that China would be purchasing up to 4 million metric tons over the next few weeks. The prices: Corn: Dec 7.51 1/2 off 8 3/4, Mar 7.58 3/4 off 5 1/4, May 7.58 off 4, Jly 7.49 3/4 off 3 1/4. Soybeans: Jan 14.48 up 1 3/4, Mar 14.41 up 6, May 14.18 1/2 up 8, Jly 14.08 1/4 off 6 1/2. Wheat: Dec 8.69 1/4 off 6 3/4, Mar 8.85 1/2 off 5 3/4, May 8.93 off 4 3/4, Jly 8.86 1/2 off 1. Oats: Dec 3.60 3/4 off 10, Mar 3.78 1/2 off 8 3/4, May 3.82 off 8, Jly 3.81 1/2 off 8.