Difference between revisions of "Chemical Safety"
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Latest revision as of 22:51, 11 May 2013
If you have a poisoning emergency, call 1-800-222-1222 in the US unless the victim has collapsed or is not breathing then call 911.
- 1 Basics
- 2 Safety Apparel
- 3 List of hazardous chemicals used in holography
- 4 Acid Safety
- Material Safety Data Sheets (MSDS) can be found very easily on the internet and also come with chemicals when you buy them. Read them. Reading a MSDS.
- Use safety glasses, gloves and an apron when mixing or handling chemicals especially strong acids or bases.
- Use dedicated containers for mixing and storing chemicals. Never use household containers that are put back in to normal everyday circulation.
- Label and if applicable date every container that has a chemical in it such that anyone else can easily identify it.
- Keep a First Aid kit close by and include a sterile eye wash bottle if possible. Better is to have an eye wash station available.
- Know how to mix your chemicals and add/mix them in the order described.
- Know how to discard your waste chemicals according to your local area.
- Never add water to acid. Always add acid to water. With strong acids like Sulfuric acid much heat is created and can boil causing an extreme splashing danger. Dilute strong acids by filling your container with water, place the container in an ice bath and stir while slowly adding the acid.
- Never work when feeling fatigued or rushed.
Goggles should be splash proof. A face mask can be worn for dangerous chemicals but must be worn with goggles. Rubber aprons are helpful for strong chemicals. Long rubber gloves will protect your hands and forearms.
For fume protection the best solution is to have a well ventelated work area. For extremely strong chemicals it may be necessary to use a respirator. Make sure the cartriges are rated for the fumes you are dealing with. (ie. Carbon for Organic solvents).
Most of the chemicals used for making holograms are safe in that you will smell them before you have suffered any damage (the threshold of detection is lower the the threshold of toxicity). For some very dangerous chemicals you can become posioned before you can smell the chemical (The threshold of toxicity is lower than the threshold of detection). For this latter class of chemicals the only solution is to have a source of external air brought into a face mask. Modern paint booths using cyanide kicked paints use a set up like this. It is only mentioned here for people who are using gasses for exotic film treatments.
Read the MSDS and choose the safety apparel accordingly.
List of hazardous chemicals used in holography
- Dichromate - Do not allow Dichromate bleaches to contact your skin. Can cause burns known as chrom holes and if inhaled can burn the nose etc.
Also there is a problem with hexavalent chromium, a carcinogen, from Dichromates,and Alodine etc used in metal coating industry getting into the ground water supply. In-situ remediation efforts can change it to trivalent chromium before disposal. One method easy enough for us in holography is to reduce the Cr(VI) to trivalent chromium with hydrogen sulfite in a low ph solution. The dichromate bleach solution generally is around ph 2.4 as given by mix formula. To Remediate the dichromate bleach solution or any chromate/dichromate solution as long as the ph is below 4 and best below 3 is to add sodium metabisulfite (metabisulfite Na2S2O5 is available at photography formulary etc) until the solution is green and then extra to be sure Na2S2O5 in water hydrolysis forms Sodium hydrogen sulfite (bisulfite) NaHSO3. The insoluble relative non-toxic chromium III hydroxide settles out as precipitate, if your willing to wait. So you can then pour off the solution and find a chemical dump etc for the precipitate. If you have a ph meter then by all means add some sodium bisulfate or sulfuric acid before hand to adjust the ph to below 3 to ensure reduction. But in the case of bleach it doesn't require this as the PH is already low. It is possible not all Cr(VI) will be reduced to Cr(III) using the acid reduction with sulfites method. With regard to the low concentration in bleach it worked quite well. Other methods of reducing using Fe(II) or Mn(II) were discussed as a remediation effort. Here is a reference to chromium chemistry including using zinc to reduce Cr(VI) to Cr(III) : Cromium Reduction
When diluting acid, add the acid to the water. Do NOT add water to the acid. If water is poured into concentrated acid, it may react very quickly causing the acid to bubble or boil. This may cause acid to be sprayed over the working area. If acid is added to water, the reaction is dispersed, and if there is a violent reaction it will spray water or dilute acid.
If you spill acid on yourself take off your gear and clothes and rinse off. There is an eye wash by the sink on the opposite side of the room of the acid fume hood. It is on a hose and can be pulled out if you need to rinse off your body and not just your eyes. Do not be shy about removing your clothes or getting water on the floor. It is better that getting an acid burn.
Required protective clothing
Goggles with a face mask over the goggles
A rubber apron draped over your front
The thin nitrile gloves with the heavier longer gloves over them. The gloves are unlikely to dissolve in the acid, but if the gloves are thin they are prone to tearing allowing acid to attack your hands through an unnoticed hole.
After pouring acid it is a good idea to clean off the bottle with wet towel. This prevents an unsuspecting person from burning themselves if they touch the bottle.
Disposing of Chemicals
Adding solvents to waste containers
Acetone, Ethanol and Isopropanol are all organic solvents. They are collected together in the plastic storage contain labeled "Non-Halogenated Solvents". The plastic is high density polyethylene: [resistance chart]. If solvents are halogenated, they get disposed of in the "Halogenated Solvents" disposal in the flammable solvents cabinet.
Disposing of full waste containers
When a waste container is full, send the slip of paper corresponding to its waste label (usually kept on the top of the flammable solvents cabinet) to the address given on the slip. Make sure to add the date. Get a box for the waste bottle (found in the stock room, on the left-hand side under the counter with the inventory computers). Put the waste container in the box, and place the box next to the door in C5. Replace the chemical waste bottle with a new empty bottle, making sure to remove or cross-out its previous label. Fill out one of the waste label slips, leaving the date empty. Place the label on the new waste container and place duplicate slip on top of the flammable solvents cabinet.
Disposing of acid
To dispose of acid we neutralize it before pouring it into the waste container. Our containers are made of HDPE and are not rated for fuming nitric acid. They are rated for concentrations of 50% acid or less. But I would still be reluctant to throw the acids away at 50% because when sulphuric acid and nitric acid are mixed they make a strong oxidizing agent and I am not sure how it will react with our container.
To neutralize the acid first dilute the acid into a larger volume of water. Then slowly add Sodium Bicarbonate until the mixture stops bubbling. We first dilute the acid to make the rate of reaction more predictable. Also make sure to use a relatively large beaker to prevent the solution from bubbling over.
If you used a paper towel throw it away into the acid waste bin under the fume hood. If you feel you got a large amount of acid on the towel you can dunk it in a solution of sodium bicarbonate and water before throwing it away.
Disposing of an empty bottle
Rinse out thoroughly. Remove or cross out label. If the bottle has a barcode, adhere to the Clark Hall inventory guidelines above. For large bottles, we typically place these on the floor next to the gas cyllinders in C5 to be later re-used as waste containers.