Hello,

The homogenenous system is contained the same phases

( oil is liquid, ethanol is liquid)

but you can say the oil is not fully miscible with ethanol that beyond to change in density and viscosity for them ........

How you can prove that?

take 5 mL from oil and transfer to volumetric flask in 10 mL size, and add 5 mL from ethanol..Now, notice is the final volume is 10 mL, you will find it less than 10 ml that proved ethanol is partial miscible with oil (oil is non polar, but ethanol has two parts one polar and other non polar.

Regards,

Dear Dohyeong Kim,

I fully agree with you, the system (alcohol + oil) is not homogeneous. This system is safely referred as pseudo-homogeneous. (it is better described as heterogeneous than homogeneous).

In optimization studies, calculations for catalyst (acidic/basic) concentration and amount of alcohol for use in esterification and transesterification reactions can be based on any of: oil, alcohol or both and must be clearly stated in the methodology; but it is usually based on the oil alone; although some authors fail to indicate the basis of their calculations and that is very bad.

It is proper to make the calculations based on the mass of oil because the oil is more stable than alcohol which is very volatile. Again, the limiting reactant is the oil not alcohol (alcohol is usually required in excess). So priority should be given to oil as basis.

But, if I may ask, why should you use acidic catalyst for transesterification? Basic catalysts are more effective dear.

Dear Luma M. Ahmed,

If the system were homogeneous, there would not have been great need for mixing in the esterification and transesterification processes. Recall that a homogeneous system or a phase has uniform properties. The system (alcohol + oil) approaches homogeneity with adequate mixing or/and addition of co-solvent.

Kind regards!

Its actually not heterogeneous system, it simply an emulsified mixture. And it slowly turns into single liquid phase as time goes by.

As far as acid concentration is concerned , try starting with 1ml of concentrated sulphuric acid for any amount of oil and slowly change the concentration according to the yield th you get in earlier case.

Good Luck Sir

Dear Gokul Raghavendra Srinivasan,

Dear Dohyeong Kim

Please note that the concept of homogeneity or heterogeneity of phases is useful to indicate instant or ease of mass transfer (as in homogeneous systems) and difficulty of mass transfer (in heterogeneous systems). If this fact is clear then, consider the case of alcohol and oil; and classify it as homo- or hetero-. Homogeneous systems do not require intense agitation or use of co-solvents; I must tell you that an emulsified mixture (as you termed it) is achieved by agitation or use of co-solvent (like detergent in the case of water and oil). Remember that emulsions are formed from immiscible phases.

Meanwhile, I never said that oil and alcohol system is strictly heterogeneous, I clearly stated that it is safely called a pseudo-homogeneous system.

Again, I wonder why you (Gokul Raghavendra Srinivasan )suggest 1 mL of conc. sulfuric acid without actually minding the quantity of oil and alcohol he is to work with (you do not even know the catalyst he wishes to use). If he intends to use microreactor system for instance, your 1 mL may be too much as a catalyst; and if he is to embark on mass production (using > 2 kg of oil for example) your 1 mL may be too little too. Catalyst concentration is usually about (approximately) 1 wt. % of the oil. It is a good practice to report clearly the basis of this concentration as I earlier stated.

Thanks and kind regards!

Dear Onyeka Stanislaus Okwundu ,

Thanks for identifying the mistake. That phrase is a typo error and its actually 1ml for every 100ml of oil.

Dear Dohyeong Kim

I hope this clears your doubts... (refer to the last paragraph of the first introductory section)

Article Comparative effect of reaction time on biodiesel production ...

Regards!