A Simple Electrical Heater
3Heating has been an issue in microscale. The spirirt burner has been very useful but not when it came to distillation. Even with anti-bumping granules, liquid would shoot over because the heating in those small vessel was not uniform. I saw very sophisticated heating mantles in Thailand and in American University equipment. I then saw the SSERC version. Here, insulated coper wire was set in plaster of Paris in a lovely wooden box. It worked well.. Well Mary, the CLEAPSSS senior technicianand I could not cope with plaster of Paris. So we went to our favourite insulating material, mineral wool (Superwool 607), but I bet cotton wool would work as well. Mary made a copper holder around which was 3 metres of insulated copper wire. This was then inserted in the small jam jar. A small bottle can be placed in the holder. A low voltege supply was attached to the wire but it must exceed 5 volts. Silicone tubing is used to connect the neck of the bottle to the delivery tube. This is work in progress but I have managed
- to distil 20% ethanol so that the fist drops coming over a flammable in water glass.
- to distil 0.1M sodium chloride so that the drops coming over give no precipitate with silver nitrate solution
- to steam distil orange peel and the drops coming over could decolourise small volumes of 0.002M potassium mangnate(VII) solution and 0,002M bromine solution, illustrating that unsaturated alkenes were in the water (limonene)
Thin-Layer Chromatography
|
|
It seems expensive. The 20x5cm plates, slica on polyester cost £70 for fifty. However, this works out at £1.40 a plate. The plates can be cut down with sharp scissors to 1x5cm plates (about 9p a plate) for use in vials or 4x5cm plates (about 28 p a plate) for use in 100 beakers covered with a Petri dish.
The use of Eppendorph tubes, to extract the colour out of leaves or biro ink on paper, limits the volume of organic solvent and the extraction can be completed by stirring with the end of blunt metal forceps. The coloured solution is applied to the plate with a fine (size 0) artist's brush. Only 0.5ml of the developing solvent is required in a vial and 2-3 ml in a 100ml beaker. If you take a photograph of a coloured chromatograph, the colours can be enhanced with software (see anthacyanins) The plates also contain a fluorescent material to detect colourless spots with UV light at 254mu (danger). |
CLEAPSS Conductivity Indicator
The conductivity indicator can tell the difference between pure (distilled, good deionised or good RO) water and supplied water. it works with a 9c battery with a resistance and LED in series with carbon fibre electrodes although copper wire and steel from paper clips work as well. When conducting there is a evidence of chemical reactions around the electrodes. The liquid drops to be tested can be placed on plastic sheet or in a plastic Petri dish mounted on the back box and held in place by Blu-tac.
This equipment is to provide evidence for the existence of ions. 1 grain of salt in water lights up the LED, sucrose in water does not.
This equipment is to provide evidence for the existence of ions. 1 grain of salt in water lights up the LED, sucrose in water does not.
Plastic pipettes and their use
 1ml, 3ml and fine-tip pipttes
The work horse is the 3 ml pipette which delivers 20 drops to the ml. This is very useful for serial dilutions. If the 1 ml pipette is used, ten more drops will be required than stsated in dome of the texts. The fin-tip pipette delivers 50 drops to the ml. This is used in titrations.
Using pipette: Have a 100-ml beaker filled with distilled or deionised water. Have a 250-ml beaker ready as the waste beaker. Keep the pipette in the 100 ml beaker. After using a chemical, suck up water from the 100-ml beaker and squirt it in the waste beaker. Repeat and leave the pipette in the beaker of water. This can all be avoided if dropping bottles are used. |
Dropping bottles
These bottles used for delivering eye drops can be labellled a the chemical. W
|
Preparing a syringe of gas
|
|
The equipment involves plastic syringes, the caps, 3-way taps and silicone tubing. I have kept hydrogen in a capped syringe for more than 5 days.
A canister or cylinder of as is the most straightforward. Basic gas preparation kits be used but always remember to throw away the first syringe of gas as this will be contaminated with air. You will require a fume cupboard for a toxic gas. if required, a silicone tube containing anhydrous calcium chloride between mineral wool can be inserted between the equipment and syringe. The Bruce Mattson method is excellent but requires practice, see http://mattson.creighton.edu/Microscale_Gas_Chemistry.html. Chlorine may begin to affect the rubber seal so needs to be used quickly |
Spirit burners
Bunsen burners are not as common in this work as spirit burners. Yet one is still able to carry out "cracking" reactions, melt lead bromide and zinc chloride, remove the water of crystallization from salts without decomposing the salt. Maany spirit burners give too large a flame but these simple home-made versions made from discarded mini jam jars (or they can bought online at about £0.5 each). The wick is thin string.
Balances
I remember that the chemical balance was the biggest expenditure in the department. They were also highly desirable by thieves. The costs were staggering but now, the digital revolution has brought the cost down and this balance on the left retails for as low as £10. In classroom manageme, the use of the balance was the rate determining step to any lesson and one use to stand over it helping the students to weigh objects. Now each group of students can have their own balance.
And yes they are accurate!
And yes they are accurate!