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• Lower Ash Content than any filter paper we have tested — less than 0.007% for quantitative grades. • Higher Alpha Cellulose Content than any filter paper we have tested—97-98% for Quantitative and qualitative grades. • No Price Premium. Your company purchasing agent pays no more for the finest. For the chemist who can specify his brand of filter papers, S & S Analytical Filter Papers offer outstanding advantages. These advantages a r e possible because of t h e skill, care and quality control methods used by S & S from selection of raws through to the finished product. Every Lot Pre-tested A substantial test portion of each batch of S & S Analytical Filter Papers is used for quality control determinations in o u r laboratories. This helps assure that you, receive filter papers uniform physically and chemically—lot after lot, month after month, year after year. Specify S&S Analytical Filter Papers for extra advantages to you in your work at no extra cost. Get the "margin of safety" in your analyses that comes with using what many chemists believe to be the finest analytical filter paper in the world. FREE
SAMPLER
Contains assortment of quantitative and qualitative grades. Also, S & S Filtration Chart, Quick Reference Catalog, table of comparative filter paper grades.
Carl Schleicher & Schuell Co. Keene, New Hampshire 44
C&EN
MAY
· 5,
Dept C-58 1958
RESEARCH
the existence of cyclobutadiene as a ligand in transition metal complexes. Sternberg points out that t h e four carbon atoms in the quinone molecule can transform in the s a m e w a y as those in cyclobutadiene and therefore the quinone molecule can form the same kind of bonds. The resulting structure can be visualized as t w o triangular pyramids base-to-base w i t h t h e iron atom at t h e center. A carbonyl group is at each apex a n d a t one of t h e three equatorial corners. The other t w o equatorial corners are occupied by the quinone ring. Quinone formation is not restricted to iron pentacarbonyl. Sternberg's group finds that a cyclopentadienyl cobalt-duroquinone complex can be formed in an entirely analagous manner. This is experimental evidence for a new method of carbon-carbon bond formation. Unsaturated molecules combine to form a conjugated system which is p a r t of a n organometallic complex. Decomposition of the complex gives the synthesized ligand as an organic compound. T h e authors suggest that this mechanism m a y be responsible for many catalytic processes including some of those of the type discovered b y Reppe.
Gamma Is Safe Foods sterilized with g a m m a r a d i a t i o n a r e nontoxic in animal tests T HE
FIRST
COMPREHENSIVE
demon-
stration t h a t gamma irradiated foods are nontoxic should hike interest in radiation sterilization to preserve foods, an Army spokesman believes. Four successive generations of rats were fed a complete diet m a d e u p of nine frozen-stored, irradiated food items, s u p p l e m e n t e d only b y nonirradiated vitamins. The results: no change in growth response, life span, or fertility. This research project's ultimate goal is to preserve food safely for long periods with a minimum of refrigeration, Merrill S. Read, chief of the Irradiated Food Branch of t h e U . S. Army Medical Nutrition Laboratory, Denver, told the American Institute of Nutrition's laboratory members at t h e Federation of American Societies for Experimental Biology's annual meeting in Philadel-
phia. Packaged foods (beef, pork, bacon, haddock, green beans, beets, peaches, powdered milk, and military cereal b a r ) with ingredients approximating a n adequate rat diet are exposed t o gamma rays from nuclear fission wastes. This kills decay-causing bacteria. Over 1600 animals took part in these tests. Half ate irradiated food; the rest ate comparably nonirradiated diets. Moreover, adds Read, t h e irradiation level was 6 million r e p , well above that necessary for sterilization. Extensive studies of six vital enzyme systems, which are believed t o be related to the metabolism of nutrients altered b y radiation, show t h a t only the cytochrome oxidase system (related to essential fatty acid metabolism) is altered. And tins system increased 10 t o 1 5 % over t h e four generations, rather than the expected decrease in activity from malfunction. This effect stems from the meat items in t h e diet, Read learned, but h e believes i t is not a deficiency. The other enzyme systems which show n o change a r e hypotonic endogenous respiration (over-all metabolism of the cell, a n d which with cytochrome oxidase is related t o essential fatty acid metabolism ) , succinic dehydrogenase (sulfhydryl system), a n d serum a n d alkaline phosphatase—both generally related t o fat metabolism in the body. Now, Read a n d his collaborators, H e r m a n Kraybill and William S. W o r t h of t h e Nutrition Laboratory and Norman F . W i t t of Colorado U n i versity, a r e studying 1 5 food items which approximate the master menu fed t o t h e Armed Forces during 1 9 5 6 and 1957. These foods will b e stored at room temperature and then cooked as normally prepared for the table before incorporation into r a t d i e t . No vitamin supplements will b e used. They will also continue studies toward understanding the observed increase in cytochrome oxidase.
"Fingerprinting" Starch A new analytical tool m a y h e l p to develop n e w starches with better properties. T w o Rutgers University (Newark) chemists, Benjamin Carroll and John W. Liskowitz, have come up with a thermogravimetric technique to probe starch mixtures quantitatively. They can determine both amylose (linear) a n d amylopectin (branched) fractions. Before, genetic researchers were hindered in their efforts to u p -
RESEARCH ent temperatures. At present, reaction kinetics are studied generally by iso thermal techniques, and changes oc curring between two test temperatures can b e missed.
Plasticizer Migration
Benjamin Carroll ( r i g h t ) , of Rutgers' Newark c a m p u s , discusses a graph on starch pyrolysis with John Liskowitz g r a d e film properties of starch for paper, textile, and surface coatings; analytical methods w e r e too costly and involved. This technique, Carroll told the Divi sion of Carbohydrate Chemistry at the ACS meeting i n San Francisco, is sim ple and general. A Testut magnetic transmission thermobalance continu ously records t h e starch pyrolysis over the entire heating range. And a pro gram controller monitors the heating to obtain a linear rate. Between t h e dehydration of the starch and t h e temperature at which '"structural water" goes off lies a tem perature region which clearly shows the difference between linear a n d branched fractions—linear fractions lose weight continuously, while i n branched mate rial the rate is considerably slower. This area ranges from 150° to 270° C , says Carroll. Other thermal regions— from 75° to 100° C , as well as from 270° to 320° C.-offer additional possi bilities for showing differences between linear and branched materials, he adds. Already, t h e Rutgers researchers have probed corn a n d potato starches, as well as modified starches such as carboxy (carboxylated or oxidized) and methyl carboxy fractions with this technique. T h i s work is sponsored in part by the Corn Industries Research Foundation, Washington, D. C. Rutgers' t e c h n i q u e also may shed more light on reaction kinetics, particu larly in t h e solid state, Carroll believes. A single pyrolysis graph can probe chemical reaction energies over the en tire temperature spectrum, and, subse quently, picks out regions of particular interest. Not only will this speed up kinetic studies, but it will pick u p en ergy changes occurring between differ-
Chemists have come u p with a definite answer t o the question of plas ticizer migration in polyvinyl acetate films. Tests show t h a t in copolymers, relatively no loss of plasticizing mono mer occurs over extended exposure pe riods. Not so with postplasticized homopolymers—plasticizer is lost fairly rapidly. T w o Borden researchers, Philip Gor don and Edward H a r m o n , told the ACS Division of Paint, Plastics, and Printing Ink Chemistry at San Fran cisco national meeting that the results of their studies show that PVAc co polymers retain the plasticizing com ponent because of chemical action. But the exterior performance of the homopolymer depends simply on the polymer properties. Their technique is simple: C 14 tags in the system. F o r the homopoly mer, plasticizer dibutyl phthalate was made from radioactive butanol. The tagged copolymer w a s prepared by polymerizing vinyl acetate with dibutyl fumarate made from radioactive butanol. After 900 hours of weatherometer exposure, the copolymer paints retained about 9 5 % of original radioactivity— a half year of outdoor weathering yielded no significant loss at all. Not so with the homopolymer: After 500 weatherometer hours, less than 4 % of the original radioactivity could b e de tected. It was a rapid loss; after the initial 100 hours, only 12% was left. Gordon notes that since dibutyl fuma rate has far lower volatility than DBP, the results must be due to migration. He emphasizes that his work is pre liminary—but it certainly indicates that the copolymer tends to maintain its polymeric structure under prolonged weathering conditions. However, some manufacturers doubt the necessity for maintaining a high degree of plasticizer retention after ini tial film formation. They cite satis factory commercial results after lengthy exposure. D u Pont, for ex ample, can point to homopolymer PVAc paint panels, still intact after six years of weathering.
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JAGUAR* IS S T E I N - H A L L G U A R
GUM!
You are certain to find that one of the 2 8 types of JAGUAR will perform b e t t e r a n d more economically than other colloids in your labo ratory — both in solving old problems and in developing new products! JAGUAR is available in 28 standard types and can be tailor-made to meet specific end use requirements JAGUAR is exclusive with Stein-Hall and is pro duced domestically in Stein-Hall plants JAGUAR produces extremely high viscosity at Sow concentrations JAGUAR is available in new types to produce low viscosities according to specifica tions JAGUAR is a cold water swelling, non-ionic type of polysaccharide JAGUAR develops its properties over a wide pH range JAGUAR has excellent thickening, film forming and stabilizing properties JAGUAR in trace quantities has excellent floc culating and filter-aid properties JAGUAR is a natural vegetable pure food colloid JAGUAR is freely available in large tonnage quantities
HALL
STEIN 285 MADISON AVENUE
^ £ | U
NEW YORK 17. Ν. Υ
Established 1866 JAGUAR, Dept. CÊN-5 Stein, Hall & Co., Inc., 285 Madison Ave., New York 17, Ν. Υ. Please send me at once 16-page descriptive booklet together with FREE sample of Stein-Hall's JAGUAR. I understand that absolutely no obligation is incurred. Name . . . Title Company Address . Zone
City
MAY
5,
1958
State.
C&EN
45
