External Standard

METHOD:

1- An External Standard is prepared as follows: 1cm³ of cyclohexane, 1 cm³ of toluene and 1 cm³ of ethylbenzene were well mixed with each other in a small conical flask and seal it with septum. This is an equivolume mixture. The external standard could contain any amount of each, as long as the amounts are known and are close to that expected in the UNKNOWN.

2- The UNKNOWN was provided.

3- Each of the pure components could be injected directly from their containers.

4- The chart recorder was set at 50mV on green scale. All changes in attenuation were achieved by altering this setting.

Samples were delivered by injection through a septum using a calibrated microsyringe.

5- 0.3µL of cyclohexane was injected at a range setting of 50mV (medium sensitivity) the peaks was given between 50-80 % full scale deflection.

If not the range was adjusted accordingly and the injection was repeated.

6- After that 0.5 µL of toluene was injected at a setting of 50mV, then 0.5 µL of ethylbenzene is added at same setting.

7- Next, 0.8 µL of the external standard( equivolume mixture) was injected followed by 0.8 µL of the unkown, both at a setting of 50mV. The three peaks was waited to appear in each case. If all the chromatograms are acceptable proceed to Promgram 2 following the key sequence shown above.

8- When the instrument had reached its new operating temperature, 0.8 µL of the external standard and an acceptable chromatogram was obrtain.

Procedure:

A distillation apparatus was assembled using a 100 mL distilling flask and a 50 mL collection flask. The collection flask was immersed up to its neck in iced water in order to minimise escape of cyclohexene vapours. 20 mL ofcyclohexanol and 5 mL of phosphoric were placed in the distilling flask and the solution was mixed thoroughly. Several boiling stones was added, and the cooling water was started in the condenser. The mixture was heated carefully until the product started to distill. The temperature was under 100 oC. The heating was stopped when there was a small volume remained in the flask.

The distillate was saturated with solid sodium chloride. The salt was added little by little and the flask was shaked gently. When salt dissolved, 10% agueous sodium bicarbonate solution was added to make the distilled solution basic to litmus.The neutralised solution was poured into a separatory funnel and the two layers were seperated. The aqueous layer was drained and then the upper cyclohexene layer was poured into a 100 mL conical flask containing a small portion of anhydrous calcium chloride. The mixture was