Chemistry Workshops to Prolong the lives-of Your avo rite ~anitors John N. Aronson State University of New York at Albany. Albany, NY 12222 Professors Shelton Bank, Jon Zubieta, and I have given periodic lecture-demonstrations to members of our university maintenance crews on the potential dangers from the chemical suhstances which thev use in relativelv routine cleanine duties. The supervisors have been rightfully concerned, since the staff uses an astounding variety of potentially hazardous chemicals every day. These training sessions have substantially reduced the dangers to which our staff is exposed. Many of the lectures and demonstrations from our workshops should be of interest to those who teach elementary chemistry courses, since several important chemical principles are illustrated. These lectures and demonstrations involve the toxic properties of the isolated chemicals, as well as their acid-base and redox reactions. Toxicity Although we do not emphasize the broad problem of toxicity, we usually begin with the admonition not to drink anything they use, to avoid chronic contact while pouring substances, and always to work in a well-ventilated space. We give them the phone number of the local medical center emergency room to contact in case of a suspected poisoning. We also make them aware of several reference hooks kept in the Chemistry Department office which deal with toxic materials and dangerous suhstances (1-4). The level of toxicity reported for petroleum distillates is somewhat surprising. Short term exposure may cause dizziness, drowsiness, headache, and nausea, with general central nervous svstem deoression. Asoiration of oetroleum distillates can cause hemorrhagic and often fatal bronchopneumonia. These are fat solvents. which affect nerve sheaths and therehv alter the function of nerves. Furniture oolishes freauentlv contain 30-60s ~ e t r o l e u m distillates, and some pressurized spray can insecticides and stainless-steel cleansers have high amounts. As a soecific exniture polish may kill them! Acid-Base Properties When we discuss the fact that many of their cleaners are chemically classified as acids or bases (alkali),we define acids simply as substances that can give up protons, lower the pH, and increase the acidity. Bases are defined as substances that can accept protons, raise the pH, and decrease the acidity. We distinguish the weak acid vinegar from the strong acid hydrochloric (muriatic) acid and classify ammonia as a weak base and sodium hydroxide and trisodium phosphate as strong bases. We explain the color changes that acids and hases produce on litmus. We then demonstrate the acid-base properties of some chemicals used by the janitors. Litmus tests are performed separately on vinegar and on ammonia. Then we dilute a few drops of toilet howl cleanser (originally 23% HCI) and also a souirt of oven cleaner (NaOH) over 100-fold and show that these two solutions are still able to produce the litmus color chanees characteristic of an acid and a base. resoectivelv. test tube and let the janitors feel the heat generated. We em1036
Journal of Chemical Education
phasize that both acids and alkalis can be good cleaners by themselves. but mixed.. thev. iust " neutralize each other. If substances are reacting with each other, they are not reacting with the dirt. Thev are told to wash their windows with ammonia or with vinegar but not with both together. Redox Properties We introduce oxidation reactions in terms of ordinary combustion with atmospheric 0;: as the oxidant and then extend the concept to include oxidation via other oxidants. The combustion lecture and demonstration are focused on the petroleum distillate products mentioned above in connection with toxicitv. The reaction between bleach and toilet bowl cleanser provides an example of an anaerobic oxidation Combustion Since the flash point of petroleum distillates is sometimes as low as 20°C. these soravs . " could he hand-held flame throwers under appropriate conditions. I have tried to convince graduate students to smoke a cigar while I sDrav toward them,-but so far, I have not been able to coerck anyone to submit to the experiment! The flammahility of a furniture polish can, however, he easily and safely demonstrated by dipping a length of cotton string into the polish, removing the soaked string from the polish, and then lighting the string with a match. A yellow flame with heavy black smoke results. The flame may then be extinguished and the unburned string which remains, inspected. Anaerobic Oxidation Hypochlorite bleach as a 5.25% solution is a potent oxidant. In theory, this bleach could cause spontaneous combustion when used in the wrone"wav.such as with steel wool or when applied to white-wall tires in which the vulcanization sulfur could be vigorously oxidized. The mixing of bleach with toilet bowl cleansers containing high amounts of HCI can generate ereen chlorine eas. This last reaction has actuallv caused a " recent death in our area. The reaction between bleach and HCI, i.e.. OCI-(aa) + HCl(aq) CI2(g) OH-(aq), may be demonstrated. mall, but visible, amounts of CI:, can be generated by adding household hypochlorite to diluted HCI in a side-arm test tuhe. The Clz gas may he conducted through the side-arm into the bottom of a second test tube for further experiments. Potential excess gas may be trapped in a third vessel. In our demonstration we showed the oxidizing properties of Cl,(g) by conducting three further experiments in the second test tube. In the first experiment, the Clz gas generated 2IC1. The is reacted with 12 according to C12(g) + I:,(aq) iodine solution is a stabilized concentrate used in cleaning our Student Health Center and is itself an oxidant. Chlorine is, of course, the more potent oxidant. The I:, solution is discolored as the reaction progresses. In the second ex~eriment.Cl.,(e) oxidizes an aaueous iodide
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+
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the characteristic blue-black starch-iodine complex will form. In the third experiment the C12 is generated into a tuhe containing water covering a copper penny. The coin becomes disfigured as the Cun is converted to cupric chloride.
Concluding Remarks ourmaintenance staff face many ,,the,. potential hazards from chemicals they use, but they can he expected to have a reasonable survival rate if they are informed and follow all procedures with caution. In particular, they are warned about mixing chemicals and about using more than the recommended amounts of chemicals. Good ventilation is especially emphasized. The workshops appear to he very effective. The cleaning staff are interested and attentive' The sessions give us an opportunity to create goodwill for the Chemistry Department.
Finally, the workshops provided several "real world examples" of acid-hase and redox reactions of organic and inorganic chemicals. Literature Cited 111 nreirharh. H. H.. , - ~ ~ ~ d h , ~P, Ok ~ X , ~prevention. ~~L: r ~ i ~ ~and~ ~~ , ~ i ~~ . ~ mhed.. L ~ ~ ~ ~ ~d vuhkstilms. iP ~ d I . , ~A I ~ % ( ' A , 1980. I21 Goaaelin. H. F. H d s e . H . C., Smmth. R. P.. and Clranm. M . N., "Clinical Toxicology orrrlmmprcial i2rwlurra.~thed..w i ~ l i n m s& w i ~ k i n s .timor more. 1381. 1x1 ~ c m t s r~. i c ~k . . a n d ~ u g h e r~.;.~hemicnl ,~. ~ w m i a o f ~ work~lxce:..~. ho B.L+ pincoft Cu., Phildrlphia. 1978. (41 ~~HazardourChemicalsDaLnB~mX~lEdi~urWeixr.C.I.N~,yerDaLnCurp..ParkRidge. N.I. 1980.
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Volume GO
Number 12 December 1983
1037
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