[HN3]

Hello
Anyone have information about using refractive index in quantitative analysis

Thanks

[chiralic]

Hello HN3:

You can do Quantitative Analysis using Refractive Index (Refractometry), below you can see
several applications where RI are used:

- Determination of the water content in milk
- Determination of protein content of aqueous solutions and of the albumin content of blood serum
- Determination of "per cent solids" - Total sugar Content in water, food, liquors, beer, sap and others
  fluids
- Determination of concentration of unsaturared oils in butter, fats, vegetable oils, and seed
- Control of the composition of glass melts
- Deterrmination of the sulfur content in rubber
- Estimation of the amount of bound styrene in GR-2 rubber
- Determination of the total aromatic content of petroleum hydrocarbons
- Determination of the amount of free fatty acid in soap
- Measurement of the salinity of sea water (also you can do it by electrochemical methods)
- Determination of the water content of alcohols and of honey

Also you can use Refractive Index to evalute equipments of Distillation and Extraction...

Regards,

Chiralic

[HN3]

tHANK you alot
but I want to know how we can use the refractive index in quantitative analysis
Thanks alot

[chiralic]

Just do a graph Parameter (Refractive Index) Vs. Concentration or what do you need exactly?
In Skoog-West book (Intrumental Analysis) you can find more information..."old" edition better

Do you have a sample?  // Do you want that I explain you a method HOW TO do it ?

Regards,

Chiralic

[HN3]

Hello
Thank you alot chiralic .
In fact, i have an organic project in my university, and i must search about this subject ( using refractive index in quantitative analysis )
I searched in the library of university,but i did not found any thing.
Exactly I want to Know the method
Thanks
(Iam sory my english is not good)

[chiralic]

Hello HN3:

My english too...Do you speak Spanish, French or Italian?

Please write down details about your project...Do you want monitoring a synthesis?
Ssend me this info into a private message

ADVICE: Search in OLD Books about Instrumental Analysis...

Regards.

Chiralic

[chiralic]

Hello HN3:

Well, I prepare some information to your project...

REFRACTOMETRY / REFRACTIVE INDEX

Quantitative Analysis (Binary mixtures and Solutions)

Binary mixtures and Solutions do not exist a general relation between the composition and the refractive index of a binary mixture of components A and B. In an ideal solution, n linearly varies with fraction m volume Va:

n= naVa + nb(1-Va) or,  n= nawa + nb(1-wa)

n: Refractive Index
V: Volume
w: weight

Three methods exist that can be used to calculate concentrations based on the determination of the refractive index:

FIRST METHOD: Using Specific Refraction

Specific refraction like property additive. This allows to establish an equation to calculate the refraction of a mixture from the refractions of soluto and dissolvent.

Z.rm = X.ra + Y.rb, where
Z: grams of the mixture, X: grams of composed A, Y grams of compound B and ra, rb, rm are the specific refractions of the compound A, compound B and Mixture respectively.

There are several formula to calculate the specific refraction (you can find these formulas on internet or in a Instrumental Analysis Book, maybe Skook:

- Lorentz-Lorenz Equation (most used)       

- Eyckman Equation      

- Newton Equation         

- Gladstone-Dale Equation      

- Edwards Equation         

SECOND METHOD: Using Clemens Method (see Ind. Eng. Chem. (1921) 13: 813) If you have
access to American Chemical Society Journals you can download this paper. Below you can find
the URL of first page of this paper:
http://pubs.acs.org/cgi-bin/abstract.cgi/iechad/1921/13/i09/f-pdf/f_ie50141a027.pdf

THIRD METHOD: Using Graph (chart solution) => refractive index vesus concentration (%w, %vol..)
Graphical representations can be made from refractive indicex versus. % in weight or % in volume.

Accoding several authors, is better use %volume than %weight, because better linearity has been observed.

Ok this is theory...let go to a practice...

Just choice for example Water and Ketone, you must prepare a set of solutions of different concentrations and them you will measure their refractive index (Temperature is very important)

To get a graph you can use Origin or Excel

I attached a "sample graph" of how is it...

Regards,

Chiralic

[chiralic]

I cann't upload the picture via this list....and you can see it on this URL:

http://i11.tinypic.com/2v8039x.jpg

Regards,

Chiralic