Literature

"What's Wrong with pH? A Conservator and a Scientist Search for Consensus," by Harald Berndt and Nancy Love. WAAC Newsletter 16 #2, May 1994, p. 14-18. (waac=Western Association for Art Conservation.)

The authors take a fresh look at ways of measuring acidity of carbohydrates. Excerpts: "pH is theoretically defined as the negative decadic logarithm of the hydrogen ion activity. This definition has no practical utility, as hydrogen ion activity depends on all other substances in the system to be evaluated. Practically, the best one can do is to use the operational definition of pH, as adopted by the National Bureau of Standards. . . . It is clear that paper does not, strictly speaking, have a pH. Only solutions equilibrated with paper can have a pH." Readings by cold extract, indicator paper and surface pH for the same six naturally aged papers are compared. Perhaps the authors rely too heavily on straw men and perhaps they take positions that appear ultra-purist, but at least they have not oversimplified anything. (3A9.7)

Appendix E from the Barrow Research Laboratory's Permanence/Durability of the Book, VII, Physical and Chemical Properties of Book Papers, 1507-1949 (Richmond, Virginia, 1974) was 50 pages long, too big to fit in the booklet, so they put it on microfiche and stuck it in a pocket in the back of the booklet. It contains the raw data from the lab's massive survey of naturally aged book papers: date of publication, MIT folds at 0.5 kg tension (across the line of print in both the inked and uninked section of the page, and with the line of print in the uninked section), tear resistance in both directions, presence or absence of calcium and aluminum, cold extraction pH in inked and uninked sections, and fiber length. A paper copy of this table is available from the Abbey Publications office for the cost of the photocopying and postage: $7.50. (3A9.8)

"Alterungsbeständigheit gestrichener Papiere: Eine Übersichtsuntersuchung (Aging Resistance of Coated Papers: A General Investigation)," by A. Proksch, H.-H. Hofer, P.C. Le and W. Knapp. A paper given at the 16th PTS (Papiertechnische Stiftung) Coating Symposium in Munich, September 1993. (In German)

At the request of the APA Editor, author Hans-H. Hofer sent a copy of the version that was delivered at the symposium; the full-length paper will appear in the proceedings later on.

The German paper permanence standard DIN 6738, with its "lifespan classes," was used to compare 18 uncoated and 33 coated papers of three sorts: acidic wood-containing paper (i.e., groundwood), neutral (i.e., alkaline) wood-containing paper and neutral freesheet. Brightness loss and yellowing due to changes in the coating binders, as well as strength loss, were investigated. Results are summarized in 21 graphs. In every case, coating raised the lifespan class of acidic wood-containing papers. With neutral wood-containing papers, improvement in lifespan class was "possible"; if it was already in the highest class, however, no improvement could be observed. All the neutral freesheet was already in the highest class, 24-85, whether it was coated or not. (3B1)

The Proceedings of the "Workshop on the Effects of Aging on Printing and Writing Papers" sponsored by ISR July 6-8 are now available for $95 (plus shipping and handling) from both ASTM and NISO Press. Among the 16 papers in the Proceedings are:

Overview of Paper Deterioration

Paper Permanence: Present Needs and Future Opportunities

The Mechanisms of Chemical Deterioration of Paper

Artificial Aging of Paper: Correlation with Natural Aging

Accelerated Aging of Paper: Can it Really Foretell the Permanence of Paper?

To order from NISO Press, call 1-800-282-NISO. (3B1)

"The Effect of Atmospheric Pollutants on Paper Permanence: A Literature Review," by Norayr Gurnagul and Xuejun Zou. Tappi Journal, July 1994, p. 199-204. 37 references, from 1926 on. They found more studies on SO₂ than on NO₂, and almost none on ozone or the interaction of the various gases. Paper containing more mechanical pulp or calcium carbonate picked up more SO₂. (3B1.23)

"Discoloration of High-Yield Pulps. I. Influence of pH and Bleaching on Spruce TMP," by Y-Z. Lai, T. Suzuki and S. Omori. Cellul. Chem. Technol. vol. 27, no. 1, Jan.-Feb. 1993, pp. 79-85. Unbleached Norwegian spruce thermomechanical pulp was found to be brightest at pH 3 to 4; bleached samples were brightest at pH 5 to 8. Bleached pulp can undergo irreversible darkening at pH 9. (3B1.4)

"The Role of Lignin in the Mechanical Permanence of Paper. Part 1: Effect of Lignin Content," by X. Zou, N. Gurnagul and T. Uesaka. J. Pulp & Paper Sci., Nov. 1993, p. J235-J239. Papers were aged at 90°C and 75% RH in sealed glass bottles for up to 30 days. All the papers were more or less acidic. The authors found that lignin contents in the range of zero to 28% do not result in greater loss of strength properties upon aging. (Most woods do not contain more than 28% lignin, so this range is nearly all-inclusive.) (3B1.7)

"Temperature Effect on Paper Recycling," by M. Nazhad and L. Paszner. Progress in Paper Recycling, v.3 #3, May 1994, p. 22-28. Heat used for drying recycled paper is known to have a strong negative effect on the fiber. Strength losses reported ranged from 10% to 34% from a single drying cycle. Results in this study agreed with previous work. The abstract says:

Drying strongly affects fiber deterioration. Heating after air drying was found to intensify the deleterious effects of recycling. The physical properties of the paper decreased and the brittleness of the fibers increased. More importantly, the effect of heat drying should not be ignored in studying the effect of recycling. (3B1.8)

"Chemical, Physical and Mechanical Properties of Common Polymers," by T. Bezigian. Paper presented at the 1993 Extrusion Coating Short Course, 4-6 May 1993 at Charleston, SC. Pages 3-44 in the preprints, published by TAPPI Press, 1993, 385 pp, $83.

This report describes and compares the common polymers used in paper coatings, with regard to their chemical and physical properties, production and preparation. Polymers described are low density polyethylene, high-density polyethylene, ethylene vinyl acetate copolymers (EVA), ionomers (such as surlyn), polypropylene, polyvinyl alcohol, polyesters, polyamides (nylon), polycarbonates and polyurethanes. (3B1.8)

Chemical Processing Aids in Papermaking: A Practical Guide. TAPPI Press, PO Box 102556, Atlanta, GA 30368 (800/332-8686). 1992. 240 pp, soft cover. Item No.: 01 01 R192; ISBN: 0-89852-256-0. $96; TAPPI members $64. Shipping in U.S. $3.15.

The uses and properties of the most common types of additives are described:

Slimicides, preservatives and microorganism control agents

Agents for controlling pitch, scale, and other nonmicrobiological deposits

Paper machine clothing, cleaning, and conditioning

Alum, acids, bases, and salts

Internal and surface sizing agents

Pigments and fillers

Retention aids, drainage aids, and flocculents

Wet strength resins

Latexes

Foam control agents

Crepeing and release aids

Softening/debonding agents

Deinking (3B1.8)

"Variations in Strength and Bonding Properties of Fines from Filler, Fiber, and Their Aggregates," by Mahendra Patel and R. Trivedi. Tappi Journal, March, 1994, p. 185-191. The authors use an expanded definition of fines to include not only ray cells and short pieces of fibers, but white-water fines, simulated fines and filler fines. Each type has a different effect on strength properties. The filler and white water fines weaken the paper, while the fiber fines, especially the smaller ones, strengthen the paper by increasing fiber-to-fiber bonding. (3B1.8)

"TRS Provides Listing of Toner Binder Sources, Plans to Unveil Ink Jet Newsletter in July." Imaging Supplies Monthly, May 1994, p. 10-11. trs=Toner Research Service, of Black Mountain, SC. John Cooper, head of TRS, publishes one newsletter, Toner Technology Monthly, and will launch Ink Jet Technology Monthly in July. Here he lists 60 sources of principal toner binders for the U.S. market.

There are nine kinds of binders, plus "miscellaneous"; "miscellaneous" is the biggest category. The others are acrylic, epoxy, EVA, polyamide, polyester, polystyrene, styrene acrylic, styrene butadiene, and wax. Some of the sources are BASF, Ciba Geigy, Dow Corning, Du Pont, Eastman Chemical, Firestone, Goodyear, Hercules Materials, Mitsubishi Rayon, Monsanto, Phillips 66, Sanyo and Union Camp. Image Polymers Co. of Wilmington, MA, leads the rest in the number of toner binders it makes: seven, counting "miscellaneous." (3B2.18)

Welcome to the World of Papermaking is a Bibliography of Papermaking for Children and Young Adults, compiled by Helen Lee. For more information write TAPPI, Technology Park/ Atlanta, Box 105113, Atlanta, GA 30348-5113. (3B3.2)

Chinesische Bambuspapierherstellung, Ein Bilderalbum aus dem 18. Jahrhundert. Kommentiert von Wolfgang Schlieder, Pan Jixing & Sybille Girmond. Akademie Verlag, Berlin, 1993. DM 295. ISBN 3-05-002369-4. 114 pp. of illustrations in b/w and color. (3B3.3)

"Alkaline Papermaking: Relying on Good Chemistry," by Janice Bottiglieri. PIMA Magazine, April 1994, p. 30, 32-35. APA editor McCrady plus eight real experts were asked to comment on a number of topics related to alkaline papermaking: problems associated with it [most are now under control], filler levels [increasing], market demands [permanent paper, recycled paper], and trends [AKD to ASA, pigmented surface size, rising pulp prices, use of film transfer size presses, TCF paper, microparticle technology, and a more global outlook]. (3B3.4)

"AKD Sizing Mechanism: A More Definitive Description" by Kyle J. Bottorff. Tappi Journal 77:4, April 1994, p. 105-116. Finally, the debate over whether AKD bonds with cellulose, and if so, how, seems to be resolving itself. At Hercules's Paper Technology Division, AKD's reactions were studied directly with solid-state carbon nuclear magnetic resonance. It formed beta-keto esters on cellulose. When it was associated with PCC, it changed into the ketone hydrolysis product. PCC and GCC with calcium hydroxide on the surface of the particles gradually changed AKD into palmitone. All this helps explain size reversion (loss of sizing after the paper comes off the machine), and may lead to better means of controlling it. (3B3.4)

"The Neutral Sizing Agent - Newly Developed Sizing Agent and the Sizing Mechanism." Japan Tappi J., v. 48 #1, Jan. 1994, p. 189-192 (in Japanese). Alpha hydroxy carboxylic acids were used with alum and showed excellent sizing efficiency. Arakawa Chemical Industries' KS-951 is a new neutral sizing agent based on these findings. It is effective over a wide pH range and, unlike alkylketene dimers, does not require curing in order to develop the sizing effect. (3B3.4; PBA Abstract # 2757)

"Progress in the Rosin Sizing of Paper," by J. Fallmann, G. Pieh and M. Sychra. Przegl. Papier, no. 12, 1993, p. 453-458. (In Polish)

Rosin dispersions, with their low demand for alum and increased pH flexibility, can be used with a calcium carbonate filler. This paper compares their performance with Sarocell 309 rosin size and Aquapel. (3B3.4; PBA abstract 2369)

"To Slip or Not to Slip? An Answer to the Question," by James Beatty. American Papermaker, April 1994, p. 31. The author recounts how Riverside Paper Corp. went about solving its "slippery paper" problem, and passes on the lessons it learned regarding a minimum level of sizing for each grade, choice of carbonate filler for the grade (PCC was best for opacity, worst for sizing efficiency), sizing (they stuck with AKD, and began emulsifying it with a cationic polymer), and other matters. (3B3.4)

"The Contribution of the Environmental Concerns with the New PAM Strength Agents," by I. Iwasa. Japan Tappi Journal, Aug. 1993, p. 18-23 (in Japanese). (1994 PBA Abstr. 631) The author describes his company's new strength agent, PAM, and gives details of NeuSize 770, which he says compares with AKD and ASA in sizing efficiency under alkaline or neutral conditions without causing deposits or slippage problems. (3B3.4)

"Satellite PCC Plant, Union Camp Mill Shift Alkaline Machines to High Gear," by Ken L. Patrick. Pulp & Paper, April 1994, p. 80, 83, 86-87. (Above the title of the article is the name of the column, "Issue Focus," and then a brief summary: "The Paper Machine: Fine-tuning of filler system, switching alkaline sizing chemistry improves paper machine runability, product performance in converting plants.")

At the Franklin mill, all four fine paper machines were converted to alkaline in early 1992 using AKD, but they were switched to ASA during the summer of 1993 because of sheet slippage problems. Mark O'Malley, No. 3 paper machine supervisor, explains why the decision was made to go alkaline. It was primarily to substitute PCC for expensive TiO2, but also because of "a growing market preference for printing paper permanence." (3B3.42)

"Use of Kaolin as a Filler in a Neutral and Alkaline Medium," by B.A. Bruno et al. Paper presented at 25th Annual Pulp & Paper Meeting, 23-27 Nov. 1992, São Paulo, Brazil. Pp. 925-936 in the preprints (São Paulo, Brazil: Associaçao Brasileira Tecnica de Celulose e Papel, 1992, 1061 pp., $60.) In Spanish.

Although high-quality kaolin is scarce in Mexico, the authors studied the potential of kaolin in neutral and alkaline processes for papermaking in Mexico. (3B3.44; 1994 PBA Abstr. 181)

"The 'Geology' of Papermaking," by Joerg A. Bleeck et al. Washington Geology, v. 21 no. 3, Nov. 1993, p. 3-8. (Published from Washington State Department of Natural Resources, Div. of Geology & Earth Resources, PO Box 47007, Olympia, WA 98504-7007.)

This is a survey of ground and precipitated calcium carbonate, how they are prepared for use and used in fillers and coatings, in the U.S. and Europe. The authors compare the tonnage of CO₂ generated and the energy consumed in the preparation of both forms of CaCO₃ filler, and find that the precipitated form uses about eight times more energy and produces nearly 13 times more carbon dioxide, when everything is taken into consideration. They give a geologically technical description of the Wauconda deposit, the source of marble mined by Columbia River Carbonates, where the first two authors work. (3B3.44)

"Utilization of Mill Residue (Sludge)." Progress in Paper Recycling v.3 #1, Nov. 1993, p. 64-70. A questionnaire survey of 100 mills indicated that average sludge production was 3-7% for paper made with virgin fiber, but 29% for deinked pulp production. Fourteen of the mills reported that their sludges were nontoxic or nonhazardous as determined by the EPA test. Analyses are given of the percent solids and ash, and their heating values. Sludge can be disposed of by landfilling, landspreading, use in construction materials, and burning. (3B3.6; PBA abstract 2099)

"Environmental Impact of Recycling in the Paper Industry," by T.A. Badar. Progress in Paper Recycling v.2 #3, 1993, p. 42 ff. The characteristics of the wastewater and chemicals found in the effluent are among the topics discussed. (3B3.6; reference from the July 1993 Tappi Journal)

"Composting Mixed Waste Paper," by E. Graves and W. Telford. Resource Recycling v.12 #3, 1993, p. 51 ff. In a North Carolina pilot trial, mixed paper waste was successfully used as the sole bulking agent for municipal wastewater sludge. Conditions in the piles remained aerobic and achieved EPA temperature levels for pathogen kills. The mixed paper waste was found to decompose thoroughly and quickly when composted properly. (3B3.6; abstract from the July 1993 Tappi Journal)

"The Manufacture of Value-Added Products from Mixed Paper Waste," by M.J. Schmenk and A.M. Springer. Paper presented at 1993 Recycling Symposium, 28 Feb.-4 Mar. 1993, New Orleans. Pp. 339-357 in the preprints (TAPPI Press, 1993, 443 pp., $72). (1993 PBA Abstr. 3665)

Much of the paper collected for recycling is mixed paper waste, which cannot be recycled because there is no way to sort it economically. This report describes a project at Miami University to develop a product in which it can be used. The result was Ecoblocks, a wood substitute for use in the construction industry. The blocks are made 50 mm thick (about half as wide as a man's hand), wet formed and press dried.

Two other abstracts in the same issue of PBA, #3622 and #3624, describe creative use of mixed waste: as composite fiber boards, and as a strengthener and filler in lightweight concrete. Still another abstract, #3623, describes the manufacture of hardboards from old newspapers, which actually are easy to recycle and are not a big problem like mixed waste. The Forest Products Lab of the USDA Forest Service was involved in all three projects. An advantage of all the products is that they do not require deinking of the paper. (3B3.6)

The "Grade Profile" in the March 1994 Pulp & Paper focuses on coated free-sheet. This page is a regular feature, covering the production volume and business aspects of various types of paper, but it includes general information as well. In the section headed "Grade Structure," it says "Coated free-sheet papers contain less than 10% mechanical (groundwood) pulp with no groundwood in Superpremium, No. 1, and No. 2 grades, and some or none in Nos. 3 and 4, and even some No. 5." The market was slow again in 1993; two machines in Warren's Westbrook mill are slated for shutdown this year. Demand is expected to rise about 5% in 1994 over 1993, especially for catalogs and commercial printing. (3B3.7)

"Closing the Loop: Engineering the Effluent-Free Mill." Special Editorial Supplement to Pulp & Paper and Pulp & Paper International. Bound into the March issue of P&P. 24 pp. A realistic overview of the technical aspects and of the problems that remain. The four editors of this report conclude their introduction by saying, "So while effluent closure may practically eliminate water discharges from future pulp and paper mills, solid-waste disposal problems will likely increase." (3B3.7)

"Low-Kappa Kraft Pulping and its Advantages," by K. Kovasin and P. Tikka. Paperi Ja Puu--Paper and Timber 75(7): 491(1993). Softwood pulps with very low kappa numbers are produced using the Superbatch cooking process, described in this paper. (3B3.8)

A.W. McKenzie's 68-page booklet, A Guide to Pulp Evaluation, is reviewed favorably by D.F. Lampard in Appita v.47 #1, on p. 7. He calls it "a compact and efficient monograph on the properties of pulp, their measurement and their relationship both to suitability for making into paper and to the quality of the manufactured paper." He recommends it as compulsory reading for everyone being trained in the techniques of pulp evaluation, and perhaps also for some who consider themselves to be already trained in that field.

McKenzie gives special attention to testing high yield pulps. For interpreting test results, he recommends graphing the measured properties in pairs over the range of beating points, and comparing the results to those obtained on a reference pulp of known quality.

Published by CSIRO Division of Forest Products (Private Bag 10, Vic. 3168, Australia), 1994. It is available free of charge within Australia and for $A25 overseas. (3B3.8)

"Effective Chip Storage Design Reduces Pulp Variation, Improves Mill Profits," by Steve Quillin. Pulp & Paper, Feb. 1994, 105-107.

The wood chips from which most pulp is manufactured are stored in great piles in the woodyard until they can be used. Fiber deterioration during extended storage is a widely recognized problem, and can result in staining, fungal and bacterial growth, physical contamination, thermal and biological degradation, even fires. Two months in a well-managed woodyard is about the maximum period during which chips can be successfully stored. The author recommends the following policies:

• Maintain pile height at a maximum of 50 ft.
• Manage pile rotation for complete periodic turnover.
• Maintain maximum internal chip pile temperature of 125°F.
• Eliminate concentration of chip fines.
• Track acetic acid level in chips. (3B3.8)

"Wood Extracts and Their Effect on the Biological Downgrading of Wood," by L.R.B. Garcia and M.G.L. Ramirez. Paper presented at the 25th Annual Pulp & Paper Meeting, 23-27 Nov. 1992 at São Paulo. Pages 379-392 in preprints (São Paulo, Brazil: Associaçao Brasileira Tecnica de Celulose e Papel, 1992. 1061 pp; $60; in Spanish).

Fungus is seen as the main cause of quality loss in logs and wood chips used for pulp manufacture. The result of fungal infection sometimes shows up in the final paper product. To discourage this, the authors prepared extracts of certain woods, using four solvents (acetone and ethanol worked best), and sprayed it on sawdust. The result was marked inhibition of fungal growth. (3B3.8)

"This White Goo Saves Trees, Makes Dessert, Dances the Charleston," by S. McCartney. Wall Street Journal, vol. XI, no. 240, 7-8 Jan. 1994, p. 1, 5. Bacterial cellulose has been developed at the University of Texas, and possible commercial applications are being discussed, including a human skin substitute, food texturizer, medical products, filters, bulletproof clothing and superabsorbents. (On p. 57 of the May 1990 PIMA Magazine, a bacterial cellulose called Cellulon, developed by Weyerhaeuser, was described. Readers were invited to call Robert Winslow at 206/924-4330 for more information. Three years later, he said it was still under development.) (3B3.84)

"Paper from the Sea," Imballaggio News Jan. 1993, p. 1 (In Italian). (PBA abstract 2758) Good strong paper has been made on an industrial scale from seaweed in Venice's lagoon. Production is cheaper, chlorine-free, and without the treatment problems of recycled paper. (3B3.84)

"Kenaf Cultivation Research and its Application Plan to [sic] Paper Making in China," by Y. Kobayashi et al. Japan Tappi Journal 47 #5, May 1993, pp. 1-11 (In Japanese). The Kenaf Association of Japan has made its assistance available to a number of kenaf pulping projects in China in the provinces of Huainan and Anhui; also to the Paper Industry Development Corp. in Beijing, acting headquarters of the Chinese kenaf project. (3B3.84; PBA abstract 4240)

"Origin of Effluent Toxicity from a Simulated BCTMP Process," by I.D. Suckling, M.F. Pasco and J.S. Gifford. Paper presented at 1993 TAPPI Environmental Conference 28-31 Mar. 1993, Boston; pp. 449-456. Two New Zealand paper research organizations identified the two primary sources of acutely toxic substances as the plug screw feeder effluent before chip impregnation and before refining, and the peroxide bleaching effluent. (3B3.85; PBA abstract 3610)

"Future Pulp Markets will Focus on Our Customer's Customer," by Ingemar Croon. Feb. 1994 Papermaker, p. 42-44. The author argues convincingly that the world pulp market is no longer a commodity market but a customer-oriented one. Although pulp is plentiful now in Finland and Sweden, and has not been so cheap since 1923, pulp mills are diversifying and filling niches that were not there ten years ago. Now the end users are looking for paper made without chlorine, or with recycled content.

The growth of thermomechanical pulp (TMP) and chemi-thermomechanical pulp (CTMP) has come to a complete standstill, the author says, because of the extremely low prices of chemical pulps and the increased use of recycled fiber. But high-yield pulps like these two will make a comeback one day because of the bulk and opacity they contribute--both important properties.

Chlorine is not used any more in Sweden, the next largest producer of pulp in the world after Canada and the U.S., because they want to have effluent-free bleach plants there; but recycling water within the plant when it contains chlorine would cause corrosion. So they use oxygen, ozone and peroxide for bleaching and get very good results, Mr. Croon says. Investment cost for a new type bleach plant is 10% lower than for the conventional kraft bleach plant. (3B3.85)

"Ubiquitous Nature of Dioxins: A Comparison of the Dioxins Content of Common Everyday Materials with That of Pulps and Papers," by R.M. Berry, C.E. Luthe and R.H. Voss. Environ. Sci. Technol. v. 27 #6, 1993, p. 1164-1168. Samples of unbleached pulp and paper from Canadian mills all contained somechlorinated dioxins and furans. Dioxins appear to be widely dispersed in the ambient environment; recycling also seems to contribute to toxicity levels. Ambient sources must be controlled as well as mill sources. (3B3.9; PBA abstract 1584)

"An Epidemic Ignored: Endometriosis Linked to Dioxin and Immunologic Dysfunction," by Marguerite Holloway. Scientific American, April 1994, p. 24, 26-27.

Endometriosis is a painful, incurable disease that affects 10% of women in their childbearing years, and is growing more common. Cells from the uterine lining wander to other parts of the abdominal cavity or lung, where they build up, then slough off, in response to estrogen levels. The immune system is often affected at the same time. There is a correlation with infertility, lupus and cancer as well.

Last November, Sherry Rier reported in Fundamental and Applied Toxicology that endometriosis had developed in 79% of female rhesus monkeys exposed to dioxin 15 years ago. These were not all megadoses: one group of monkeys received only five parts per trillion (ppt) of TCDD, the most potent dioxin. The average person has about seven ppt of TCDD in their body. Similar results have been found by other researchers for PCBs, which also affect both the endocrine and the immune system. (3B3.9)

"Strong Views on Origins of Cancer," by Jane E. Brody. An interview with Bruce N. Ames in the New York Times, July 5, 1994.

Ames invented the leading lab test to screen chemicals for their ability to damage genes (the Ames test). He is a biochemist and molecular biologist at the the University of California at Berkeley, where he directs the National Institute of Environmental Health Sciences Center, and has won many national and international honors. He gets impatient, very impatient, with environmentalists who "are forever issuing scare reports based on very shallow science," especially reports about man-made chemicals and pesticides. This is what he has to say on those topics:

"99.9 percent of the toxic chemicals we're exposed to are completely natural--you consume about 50 toxic chemicals whenever you eat a plant."

"Nearly half of all natural chemicals tested, like half of synthetic chemicals, are carcinogenic in rodents when given at high doses."

In a related story, the Chicago Tribune for July 12 (p. 4) reported that three Greenpeace activists climbed halfway up the Time-Life Building in New York to hang a giant banner that said, "Chlorine Kills - Take the Poison out of Paper." Ames's opinion on chlorine as a poison is a matter of record: "Nearly all the polluted wells in the U.S. seem less of a hazard than chlorinated tap water." (He does not seem to have gone on record about the use of chlorine for papermaking.) (3B3.9)

"Bleaching and its Environmental Consequences," by D. Stromqvist. Paper presented at World Pulp and Paper, 14-15 Dec. 1992, London. 4 pp. [London: Financial Times Conferences, 1992, 181 pp., £210 (676)(7898)] Work at Eka Nobel, Sweden, indicates that pulp bleached with chlorine dioxide has as little impact on the environment as totally chlorine-free pulp. The pulp industry must recycle bleach plant effluent completely, to avoid the larger expense of eliminating all chloroorganics. (3B3.91; PBA abstract 3471)