Assembly scheme of medical experimental instruments and equipment

(1) The experimental device for heating oxygen with potassium permanganate needs alcohol lamp because the reaction needs heating. The test tube is a reaction container, the iron frame is used to fix the test tube, the gas cylinder and ground glass are used to collect oxygen, and the air duct is used to guide air.

So the answer is: ABD；;

(2) The fixed position is located at one third of the test tube mouth. When fixing the test tube, the mouth of the test tube should be slightly inclined downward. This is because the wet water contained in the medicine potassium permanganate flows to the catheter in the form of steam during heating, and it will condense into water drops when it meets the mouth of the test tube with low temperature. If the mouth of the test tube is upward, water will flow back to the bottom of the test tube with high temperature, which will cause the bottom of the test tube to burst due to sudden cooling.

So the answer is: the iron clip is clamped in the middle and upper part of the test tube, and the mouth of the test tube is slightly inclined downward.