Subject: Re: Chlorophyll experiment - Help!

From: [email-masked] (Jed)
Date: Wed, 18 Oct 1995 15:13:38 GMT

In article <[email-masked]> [email-masked] (Neil Emery) writes:
>From: [email-masked] (Neil Emery)
>Subject: Re: Chlorophyll experiment - Help!
>Date: 13 Oct 1995 09:30:53 GMT

>>I'm a 7th grade student doing a science project on the amount of 
>>chlorophyll in different tree leaves.  I am trying to find a way 
>>to best determine the relative amounts of chlorophyll between 
>>different species.  I have tried extracting the chlorophyll by 
>>using one inch square samples placed in 5 ml. of alcohol and 
>>boiled for 10 minutes.  Although I noticed a color difference, I 
>>really have no way of determining the amount of chlorophyll.
>Jennifer

Assuming you do not have access to a spectrophotometer, you will have to 
make some assumptions and do a semi-quantitative analysis.  Assume that leaf 
tinctures contain only chlorophyll (you might want to find a reference to 
see if other pigments, such as carotenoids are going to be a problem).  Do 
all of your extractions together.  Assign the greenest extract a 5, the 
second greenest a 4, etc.  If two extracts look the same and are both as 
green as the greenest, give both a 5 and so on.  Or if you can buy some 
chlorophyll and make up a standard solution the concentration of which you 
know, you could estimate the chlorophyll concentration based on the standard 
solution.  A spectrophotometer takes the subjectiveness of human color 
vision out of the process.  But assuming you have "normal" color vision, you 
can still make your project somewhat quantitative even if your eye is less 
precise than the spectrophotometer.  You might want to have another "normal" 
person rate the colors while you do it, but without the two of you 
discussing your ratings, i.e., explain to them exactly how you are rating 
them, but each person then rates the greens independently of the other 
without discussion.

>This can be done quite easily by measuring light transmitted through 
>youralcohol extracts at the proper wavelengths. It would be a matter of...

rest deleted

      

      / \ 
    í// \\  
   */// \\\*
   //// \\\\*
  ///// \\\\\
      | |
      | |
      | |
      | |
"Stay in your own cubicle, please."

Some historians attribute this remark to Mark Twain, however, it's 
actually from Matt Groenig.