How to be a Successful Organic Chemist

7 Let us have a closer look at how a SDS is formatted. The SDS for any given compound is typically organized into several categories, such as hazards, toxicity, composition, and first aid measures, to name a few. The information found in a SDS can be misleading if misinterpreted. As an example, let us examine the SDS of sodium chloride (NaCl), which is table salt. Under category 4, which is first-aid information, the SDS states that if the substance is in contact with skin to “Wash off with soap and plenty of water. Consult a physician.”That seems ridiculous. I doubt that any of us call a physician if we get salt on our fingers while we are eating fries, but the restaurant cook who is dipping their fingers into a bowl of salt eight hours a day might wonder if it will cause any harmful effects. The SDS also lists information about the “acute toxicity” of sodium chloride. The data stated is LD 50 Oral Rat 3,550 mg/kg. How does one interpret this? LD 50 Oral Rat refers to the amount of salt that will kill 50% of the rats who swallow it. Because rats come in all sizes, the amount is expressed as ratio between mass of compound and mass of rate. In this case, 3550 mg (or 3.55 g) of sodium chloride will kill 50% of rats who weigh 1kg. If we assume that human bodies work like rats, we can find a lethal dose for half a population of humans. If we assume that a human weigh 100 lb (which is a convenient number) or 45.4 kg, then 45.4 x 3.55 = 161 g NaCl might be lethal to 50% of the humans who swallow it. 161 g is over 1/3 lb of salt, so the fries would probably kill you before the salt did, but there is how you interpret this figure. As you can see from this example, the reliable information in the SDS has to be worked out ina realistic context. In this particular case, we have learned that sodium chloride can be lethal if ingested in (relatively) large amounts. Here are some of the hazards categories that SDS frequently identify for organic chemicals, and some notes about each category to help you get started. Please note that this list is not exhaustive. Table 1. Some common safety categories Category Type What does it mean? Additional comments. Flammable Physical A liquid, gas, solid or solution is flammable. Usually a spark or Most organic liquids are flammable, so the risk of starting a fire is always present and necessary steps must always be taken to avoid such risks. Oxidizing Physical The compound is a strong oxidant. If you mix an oxidant with a reductant, usually a strongly exothermic reaction happens. Care should be taken to avoid this. Some oxidizers must also be disposed of in a particular way. Pyrophoric Physical The compound ignites spontaneously in contact with air. Pyrophoric substances are very dangerous, and usually require handling in inert gas. Toxicity Health A substance is toxic.This category is vast, and requires specific Most organic molecules are toxic by numerous modes. We have dedicated a separate section to toxicity below this table. Skin irritation Health A substance irritates the skin and/ or mucus membranes Most organic chemicals irritate the skin. If the compounds are solids, gloves often offer sufficient protection, assuming the substances do not permeate Eye irritation /damage Health A substance irritates or permanently damages the eye Because the eye is so delicate,most chemicals and substances damage the eye. One of the most basic safety feature of any lab, is that the people working Carcinogen Health A substance that is suspected or known to cause cancer in mammalian cells. This is a very important category, as substances that are either suspected or known carcinogens must be handled with extreme care. It is important to note the two subcategories of suspected and known. In practical lab work, you should deal with both these chemicals the same way: very carefully Reproductive toxicity Health The substance damages the reproductive system This is a very important category, as chemicals that damages the reproductive system can have very detrimental effects.