chemical vignettes ROBERT C. BRASTED University of Minneroto Minneapols, 55455
"Instant Coral," Jugoslavian Style
A magnificent combination of underwater beaut,y and solution chemistry is observable in one of nature's wonderlands, the PlitviEka Jezera (lakes) country a hundred miles south of Zagreb in Jugoslovia. Here are located a chain of some 15 lakes with coral-like deposits in a sylvan mountain setting with each lake feeding water to the one below by a system of water falls. The total lowering is not more than 50 m, but each water fall has an individual beauty with a drop that may be as small as several meters or as much as 20 m. There are some who will justifiably question not only the travelog introduction to a Chemical Vignette but also the aquatic biology of "coral" formation. The column editor hopefully can explain the latter and pleads journalistic license for the former. The water feeding into the first lake is part of an underground system that provides a magnificent example of metal salt equilibrium. Almost any general text of chemistry will provide the fundamental concepts of water hardness, but the stress is usually on boiling the temporarily hard water to deposite CaC03 while releasing COr from the dissolved Ca(HC03)*. Or, that over the centuries stalagtites and stalagmites grow in caves, for basically the same reason (the former having to st,ick "tite" to the roof or they will fall off, while the latter "mite" grow big enough to reach t,he ceiling and then again they "mite" not, which indicztes the low degree of geological training on the part of your column editor). These PlitviEka waters come out of their limestone underground beds so charged with Cot and loaded with Ca(HCO& that the time factor for depositing calcium carbonate is more in the hour range than the century. Twigs, limbs, rocks, and even grass coming in contact with the vater are soon coated with a white carbonate deposit. The lake bottom and shore are white with the encrustation. Just as do many of t,he mineral baths of the continent so do these lakes literally effervesceCOi when the water is agitated. I t seems that the lower lakes exhibit a slower carbonate deposition rate than that found in the upper lakes, however, an equilibrium is established as the water flow progresses, since the stream and lake beds (at times 10-20 m in lake depth) are limestone.
The purpose of "Chemied Vignettes" is to illustrste applications of chemistry, especially in engineering and other scientific areas. Readers are encouraged to send items appropriate to this column to the author.
608 / Journal of Chemical Education
The color of the water is a distinctive green color due to an algae that flourishes in these hydrogencarbonatecharged waters. The concentration is not so great that trout cannot survive since many of the good eating size are observed (without a white crust). An earlier Vignette pointed out a not-so-pleasant or beautiful natural phenomenon associated with underground waters coming from mine areas. Sulfides provided not only undesirable deposits but odor and taste to waters. Here we have somewhat similar chemistry but a much more ast,hetic result.
An Unwanted Head on a Fine Body (of Water) Your column editor, over the winter, spring, and summer of 1971 has been seeking out Vignette material in the lovely country of Germany inhabited by great people who brew and ferment great beverages. The foam associated with one of these provides the head on a fine body of a brew, but another head is now presenting itself as an ever-increasing nuisance (perhaps a major problem, eventually) to the river boat traffic on such picturesque bodies of water as the Neckar and Rhein. Most of us are aware of the environmental problem of detergent effluents polluting the streams and rivers in our own country and have been quite aware of the foam developing a t the foot of falls. I t is no comfort whatsoever to see a similar stage of pollution in another country, but such is certainly the case. The quantities of detergents emptying into the German river system is painfully evident in the lock system vital to transportation in this country, raising and lowering the passenger and cargo carriers. The water flowing through the conduits from the upper to the lower levels is agitated sufficiently to cause a head of froth in the lock of such a magnitude that the portholes of boats are obscured and decks of the barges coated. After raising a boat the lock may have the appearance of a 'ktein" that only Paul Bunyan could appreciate. This foam continues on down stream for kilometers not only modifying the appearance of an otherwise beautiful river but affecting the aquatic life. It is to the credit of the mass communication media in Germany that the people are being educated on the problem of detergents as well as the even more serious pollution of the large body of water, the Bodensee. Only time will tell whether necessary corrective measures can be taken in the form of more effective sewage treatment, marketing of the proper kinds of degradeable detergents or a t least the creation of foam dispersing agent to protect the portholes.
