Kjeldahl Distillation Unit

KJELDAHL DISTILLATION UNIT 1 & 21. Dropping funnel to add sodium hydroxide, digested sample and distilled water
2. Kjeldahl Trap
3. Coil condenser
4. Siphoning tube
5. Cabinet
6. Waste discharge
7. Conical flask
8. Glass tube to hold digested sample
9. Outer jacket to hold the spent liquid after the experiment
10. Additional funnel to add distilled water
11. Steam generator
12. Quartz heater
13. Steam inlet tube
14. Cooling water inlet
15. Hot water outlet
16. Waste water discharge

Kjeldahl Distillation Unit

1. Check the distilled water level in the steam generator (11).

2. Start the cooling water circulation in the condenser (3).

3. Dilute the digested sample with distilled water (10 – 20 ml) and load it in to the inner glass tube (8) through the dropping funnel (1).

4. Take 25 ml of boric acid solution with indicator in 250 ml conical flask and place it at the receiver end (7).

5. Take 40 ml on 40% alkali and keep it ready in the dropping funnel (1) with stopcock closed.

6. Check to ascertain that all the rubber tubing is tightly fitted.

7. Now start the steam generator by switching ON the heater.

8. The steam generator will now generate steam which passes through the outer jacket tube (9) and then bubble into the inner tube (8) which holds the sample.

9. When the steam bubbles vigorously with the digested sample add 40 ml of alkali “immediately” and close the stop cock.

10. Now the digested sample in the inner tube (8) turns dark brown.

11. Continue the steam distillation until liquid ammonia collects in the boric acid solution. There will be colour change based on the indicator used. Usually it will be red to green. Collect 100 – 120 ml distillate in the conical flask.

12. Switch off the heater and then remove the conical flask and titrate the solution using a burette.

13. Now stop the cooling water circulation in the condenser.

14. Once the heater is switched off, the digested sample automatically gets siphoned into the outer jacket (9) through the siphoning tube (8).

15. Add distilled water once or twice to rinse and remove the spent reagent which might be present in the inner tube.

17. The spent reagents which is collected in the outer jacket tube (9) can later be removed by opening the pinch cock and the next experiment can be started. Normally it takes 5 to 7 minutes for distillation of one sample.