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Nitric acid is usually sold in concentrated form as a liquid which is extremely corrosive, very poisonous, constantly gives off acid corrosive fumes, and in contact with many metals such as silver or copper gives off a brown gas called nitric oxide which is also very poisonous. Under the action of light it slowly decomposes into oxides of nitrogen plus some free oxygen, and may thus produce a pressure in a stoppered container. If kept for any time, the stopper should be occasionally loosened (Carefully!) to avoid pressure build up. It will cause burns in contact with human skin, so if nitric acid contacts the body it should be flooded with a copious stream of cold water. Spills should be covered with a thick layer of solid sodium bicarbonate, which after no further bubbling is seen, may be swept up and preferably scattered over the ground and covered with a layer of soil, where it will do no further harm, having become a fertilizer; sodium nitrate. Do not pour acid down the toilet or a drain. Do not use newspaper or paper towels to mop up spills; it is possible they may spontaneously catch fire. Mopping up spills with sawdust is similarly dangerous. Concentrated nitric acid should be kept in a dark place in glass, polythene or polypropylene bottles, either glass stoppered or stoppered with proper plastic (polythene) stoppers made for the purpose. It will rapidly destroy corks and rubber bungs. Plastic containers must be strong and rigid, not at all like the plastic milk or soft drink bottles. It is safest to wear a proper respirator designed to protect against acid gases and fumes and to wear plastic - not rubber - protective gloves; a plastic apron is a good idea too, as nitric acid quickly rots clothing. Protective eyewear is essential. When diluting concentrated nitric acid, it is necessary to perform the operation in a well ventilated place, or in the open. Pour over half of the water needed into a plastic or glass container, then add the acid slowly with constant stirring, using a glass rod or piece of stiff plastic - even lucite. A little heat may be generated, but insufficient to produce boiling or spurting. Finally, add the rest of the water and stir well and stopper. Try not to re-use bottles which have contained food items, and store well away from children. It is most important to label everything, and even more important when poisons or corrosive materials are concerned. The acid will slowly destroy paper labels, but covering paper labels with transparent, adhesive polythene tape will help preserve them. Black Marker Pen can be used with very bold, clear lettering and will survive for quite a while, though colours will fade more quickly. Pour out the acid in such a way that the inevitable drips will not contact the label, and wipe the bottle carefully with a damp cloth after re-stoppering. Finally, having said all that scary stuff, bear in mind that one of my first jobs as a lab boy at age 14 was to dilute strong acids in five gallon quantities at a time, and to keep the hundreds of laboratory reagent bottles all topped up every morning. They weren't concerned with safety in those days, so we got no protective clothing, etc - other than the raggedy lab coats departing students left behind! Didn't I ever have accidents? Of course I did, but I'm now nearly 81. If you are lucky you draw a pension as a prize for surviving! Cheers for now, John Burgess Mapua, Nelson NZ |
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