Health and Safety Issues
The chemicals used in making biodiesel are dangerous, and if they are used without precaution can cause serious injury or even death. Please don't believe ANY biodiesel website that claims no-one has ever been injured making biodiesel, because they have. Please be careful at all times and make sure you are in a well ventilated area or preferably outside, away from any flammable sources, with access to clean running water. Don't allow children or pets anywhere near where you intend making biodiesel. Always wear proper protective gloves, an apron, eye protection and preferably a full face mask, and do NOT inhale any vapors or sniff any fumes.
Methanol can cause nausea, dizziness and visual disturbances that can result in blindness and even death, and it doesn't even need to be swallowed to do this because it can be absorbed through the skin or by breathing in the vapour. Swallowing small quantities could pose a significant health threat to the central nervous system, and could also affect other vital organs (drinking 10ml would cause blindness, and 100ml would in fact cause death). It is a cumulative poison too, and so repeated exposure to relatively low concentrations could cause harm in the long run. Always wear a suitable dust mask when working with methanol, and note that that cartridge respirators are not suitable.
Sodium hydroxide - NaOH, also known as caustic soda and lye, can cause severe burns to the skin and can be particularly damaging to the eyes. Stirring can produce a fine mist of liquid droplets which, if inhaled, causes severe irritation of the respiratory tract and breathlessness can occur. Accidental swallowing can cause major damage to the throat lining and digestive system. It reacts with aluminum (producing flammable hydrogen gas), tin and zinc, so use either glass, enamel or preferably stainless steel containers when using this chemical. Sodium hydroxide absorbs relatively large amounts of water when exposed to the atmosphere and will eventually dissolve in the water it absorbs. It should therefore always be stored in an airtight container.
Potassium Hydroxide - KOH, also known as potash, is a very caustic, extremely alkaline substance. Although it has been used as a baking aid similar to baking soda, it shares many of the same dangers as that of sodium hydroxide regarding potential irritation to skin, eyes, airways and digestive system. Similarly, it also reacts with aluminium to form explosive hydrogen gas. It should be stored in an airtight container because it too readily absorbs moisture from the atmosphere.
Sodium methoxide, created when methanol and sodium hydroxide are mixed, is an extremely toxic, caustic chemical that produces extremely poisonous and flammable fumes. If sodium methoxide comes into contact with skin it will burn without even being felt, as it will kill the nerve endings. In such a situation, wash immediately with lots of clean water. Always have a hose running when working with sodium methoxide, and only ever make as much as is intended to be used immediately, rather than storing it. Sodium methoxide is also very corrosive to paints, so watch your surfaces.
Potassium ethoxide, created when ethanol and potassium hydroxide are mixed, is also an extremely toxic, caustic chemical that produces extremely poisonous and flammable fumes. It will cause irritation and burns to the skin, and immediate or delayed severe caustic burns to the eyes, although if the skin and air are dry no reaction may be noticed on skin. Inhaling will cause sneezing, irritation and burns. If ingested, medical assistance should be sought immediately.
Isopropyl Alcohol, used in the titration test on waste vegetable oil, is relatively non-toxic and evaporates quickly, although like most chemicals it is poisonous if swallowed. The vapours it produces are denser than air and are highly flammable (so keep it away from heat sources and open flames). A combination of water and propene, it is often sold as a solvent and a cleaning fluid, such as rubbing alcohol for cleaning houshold items such as glasses, computer monitors, etc. Avoid letting it come into contact with your skin. Long term contact with the skin can lead to defatting, a condition similar to dermatitis.
Mixing the Reactants
The alcohol and the catalyst (methanol/ethanol and sodium hydroxide/potassium hydroxide) should only ever be mixed in a suitable, SEALED container. NEVER mix sodium methoxide in a plastic container because it will eventually eat it (by attracting particles away). Also, NEVER use an electric drill in order to mix faster because sodium methoxide fumes are flammable.