Open tube test

White White sublimates could be either ammonium salts or As O, or Sb O, or lead chloride or Hg Clj. Repeat the test adding five times the amount of dry sodium carbonate to the assay, ammonium salts give off ammonia (NH,) while mercury chloride decomposes to metalhc mercury. T o distinguish between As- and Sb-oxides use the open tube test. 

Table 12.12. Open tube test characteristics Element Reaction...

Sfi.F-TeST 4.2A What is the pressure in a system when the mercury level in the system-side column in an open-tube mercury manometer is 25 mm lower than the mercury level in the atmosphere-side column and the atmospheric pressure corresponds to 760. mmHg at 15°C ... 

If the measuring points are chosen far enough away from the ends of the test vessel so that end effects are negligible, this expression may be used with confidence. Bischoff and Levenspiel (12) have presented design charts that permit one to locate monitoring stations so as to avoid end effects. For example, in a packed bed reactor with a tube to pellet diameter ratio of 15, where the packed bed is followed by an open tube, at least 8 pellet diameters are required between the measurement point and the open tube if errors below 1% are to be obtained. 

Close the test tube under the water with your thumb, extract it from the bath, wrap it in a towel, bring it up to the flame of a burner and, after opening the test tube, light the gas mixture. What happens ... 

FILL PINT CAN ONE QUARTER FULL OF HOUSEHOLD AMMONIA. FIT STOPPER WITH 6" GLASS TUBE IN OPENING. PLACE TEST TUBE OVER GLASS TUBE. HEAT CAN OVER LOW FLAME. TEST TUBE IS FULL OF AMMONIA WHEN MOIST, RED LITMUS PAPER HELD AT ITS MOUTH TURNS BLUE. 

REMOVE A FILLED TEST TUBE FROM GAS GENERATOR CAN. MOUTH DOWN. CLOSE MOUTH OF TUBE WITH THUMB. OPEN TUBE UNDER WATER. AMMONIA DI5-SOLVES EASILY, WATER RUSHES IN AND FILLS TUBE. 

Nitroalcohols 3a-j were isolated in good yields when a mixture of aromatic aldehydes 1 (10 mmol) and nitro compound 2 (10 mmol) adsorbed on Si02 (finer than 200 mesh, 5 g) and taken in a open Pyrex test tube was subjected to micro-wave irradiation in a domestic microwave oven (BPL, BMO 700T) at an out-put of about 600 W. After cooling the reaction mass to room temperature, the products were isolated by extracting with dichloromethane and evaporation of the sol-... 

Separation by chromatography test tubes, pipet, beaker, capillary tubes or open tubes or burets, ion exchange resin or silica gel (or filter paper strips, with heat lamp or blow dryer)... 

Be careful to point the opening of test tubes away from yourself or others. 

Problem In order to discuss the reaction with air as an important component, one could heat the copper without air in an evacuated test tube copper remains unchanged after heating in the vacuum. Immediately after this, air is introduced by opening the test tube in the same moment hot copper turns to black copper oxide. With this experiment students should be convinced that the air is responsible for forming the new substance by a chemical reaction. 

It is important to discriminate the deflagration process from a normal combustion which, at first sight, seems to be problematic if the deflagration of a liquid is initiated with an open flame. But quite on the contrary, the tube test allows this very unequivocally, as the liquid level with the reactive zone close to its surface drops in the course of the experiments and an easily visible spatial separation develops between the reaction and the combustion zone. 

---