h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

In that case, how do you chromatograph leaves grass etc?

Sounds like fun - might get my Year 9's to have a go next week.

B

P.S. Did you notice the 'vlack spral onb' in post 35?

(Perhaps I should make a GE from my typos and set it as a quiz for people to guess what my intention was)

'In that case, how do you chromatograph leaves grass etc?'

I'll get back to you in a bit on this. Got to get my to the garage before 11.00 to have some minor faults put right under warranty.

Chromatography of grass/leaf exreacts

Preparation of extract:

Carefully crush some fresh grass (or autumn leaves) in a pestle and mortar with about 5 ml of propanone.

Two methods:

(i) Radial chromatography
(ii) vertical chromatography

(i) Radial. (i)a. Place a clean filter paper horizontally over an evaporating basin. Apply a spot of extract into the centre of the paper and dry with a hair dryer. Repeat for several applications of spots until you have a fairly intense spot of colour in the centre. Develop the chromatogram by carefull dropping propanone onto the centre and allowing to dry between each drop,

(i) b. (Horizontal)Performed by allowing the extract solution to creap up a 'tongue' of filter paper, which itself is placed horizontally ocross a beaker.

1. Select a filter paper circle of a size which will rest across the top of a small beaker (50ml or 100 ml)
2. Cut a 'tongue' in the filter paper about 0.5 cm width, which goes from periphery to centre.Fold the tongue down and rest the filter paper acrtoss the beaker.
3. Take 1 drop of the leaf extract and place it in the centre of the F/P at the point where the 'togue' starts. Allow it to dry and make multiple applications as described above.
4. Put just enough propanone into the bkr to reach the tip of the 'tongue', and alow the chromatogram to develope.
5. The result should be concentric circles of plant pigments emanating from the centre.

(ii) Vertical Chromatography.

IN this case, use a small rectangular piece of F/P.

1. Sellotape its top end to a pencil so that it can rest across the top of, say, a 250 ml bkr. The edges of the paper must not touch the beaker otherwise one gets 'edge effects'.
2. Draw a faint pencil line across the F/P omne cm from its bottom end.
3. Mark X's along the line at ca 1cm intervals. (This is where you'll place spots of extract)
4. Place drops of various extracts (e.g. grass, green tree leaves, yellow autumn leaves, orange autumn leaves, red autumn leaves, brown autumn leaves etc) onto the X's, using multiple applications and dring after each application as describved above.
4. Place 1 cm depth of popanone into the bkr, place the paper across the bkr and allow to develop.
5. Record the results.

Results.

For grass; yellow xanthophyll travels the furthest, followed by green chlorophyll and finally orange carotene.

(Think I might write a GE on the Chemistry of Autumn Colours').

P.S. Do you want to sent me a blank videotape, and I'll record the reactions of Group 1 metals with water for you.

No - I must have them on PC format (MPEG or AVI or whatever). We've got them on video somewhere, but it's a drag to set the whole thing when all any of us want to watch is a couple of big explosions.

B

Wish I had computer/data projector facilities in my labs. I would just love to have the stuff permanently set up and be able to seamlessly intergrate the occasional picture into my lesson, even at a moments notice e.g. if s'thing unexpected crops up in class discussion.

I dunno about seamlessly. My classes are quite accustomed to watching me search through endless menus and sub-directories ("Try the 'Science' one, Sir!") looking for an animation fo continental drift, or a diagram of the carbon cycle, or whatever it is that I've just thought might facilitate my lesson.

B