The melting transition of the magnesium salt of DNA has been systematically examined in the presence of various types of anions. The addition of ClO4- to a concentration of 3.0 N results in the biphasic optical transition, with the first phase exhibiting rapid reversibility and independence of the DNA concentration. This subtransition, which is interpreted as an intramolecular condensation to a collapsed form of DNA, is followed by a DNA concentration-dependent aggregation reaction. The aggregation can be reversed by increasing the ClO4- concentration to 6.0 N while elevating the temperature to post-transition levels. Alternatively, both the collapse and the aggregation can be prevented by melting in the presence of trichloroacetate, the most strongly chaotropic solvent for DNA which has been reported (K. Hamaguchi and E. P. Geiduschek (1962), J. Am. Chem. Soc. 84, 1329). The forces responsible for mediating both the collapse and the aggregation are superficially similar to those involved in maintaining duplex stability. The collapsed form, in particular, possibly possesses features in common with the condensed structures which can be produced in aqueous solution of certain polymers, such as polyethylene glycol (Lerman, L.S. (1971), Proc. Natl. Acad. Sci. U.S.A. 68, 1886).

A promising technique emphasised in the proposed tannery waste treatment system is surface adsorption. Specific surface adsorption processes studied were foam separation without additives, adsorbing colloid flotation, carbon adsorption, and adsorption flotation. Results show that foam separation without additives is not a feasible process for the removal of either dissolved organics or suspended solids from tannery wastes. Adsorbing colloid flotation is feasible for the primary treatment of tannery wastes, provided that dimethyldihydrogenated-tallow ammonium chloride or the like is used as a collector. Secondary treatment of tannery effluent by carbon adsorption alone is not sufficient. However, by combining carbon adsorption and flotation into a single process (adsorption flotation) a high fractional removal of both dissolved and suspended pollutants can be achieved.

tropolystyrene. Typical Dumas nitrogen analyses were in the range 9.23-9.41%; theory 9.39%.In the preferred method a solution of polystyrene (0.8-1.0 M) in methylene chloride at 5 °C was treated with mixed acid (HNO3 36.0, H2SO4 52.5, H20 11.5 wt %) containing 2.0 mol of nitric acid over 10 min. The mixture was then brought to reflux (40 °C). The nitro polymer precipitated in about 5 min. The mixture was held at reflux for 2-4 h, and the methylene chloride was decanted from the polymer. The solvent can be reused directly. The polymer was washed three times with methylene chloride and three times with hot water prior to analysis, which showed 99.0% of mononitration.Nitric Acid Oxidations. The nitrated bibenzyl (or diphenylpropane) mixtures were oxidized by heating 0.1 mol of nitro compound, 0.5 mol of 70% nitric acid, and 160 mL of water in a titanium-lined shaker tube at 180 °C for 5-6 h. The crude product was collected on a filter, washed with water, then dissolved in dilute sodium bicarbonate or ammonia solution to permit separation of about 1 g of deep yellow neutral material, mp 130-190 °C, a mixture of starting material with dinitrobenzyl. The filtrate was acidified to yield p-nitrobenzoic acid. From pure 4,4,-dinitrobibenzyl, 27.0 g, 81% was obtained, mp 243.5-244.5 °C. Dinitrodiphenylpropane was oxidized similarly to 41% of p-nitrobenzoic acid.Nitropolystyrene was oxidized similarly, but it was then discovered that 10-20% of the p-nitrobenzoic acid was destroyed during the prolonged treatment. Presumably, the yields in the preceding paragraph could have been higher with shorter contact times. Optimum yields were obtained by accepting less than quantitative conversions. Nitropolystyrene was heated with 22.2% HNO3 (6.4 mol per ring) for 1 h at 180 °C. Product isolation as described above gave 20-30% of neutral material (which can be recycled) and 87-89% of pnitrobenzoic acid (corrected for unoxidized starting nitropolystyrene). Oxidation at 150 °C, 6 h or 210 °C, 1 h, was much less satisfactory. With 11% nitric acid, the oxidation was very sluggish.Literature Cited

SUMMARY – Michigan‐grown Kennebec and Sebago potato tubers were exposed to gamma irradiation in the dose range of 0 to 400 Krad and subsequently stored in atmospheres containing 0.03% to 15% CO2. Upon illumination with 3,000 lux for periods up to 20 days while maintaining the atmosphere, all tubers developed some greening. The tubers exposed to 200 and 400 Krad were inhibited from greening to the highest degree but suffered general quality loss. The levels of 10 to 20 Krad, which are suitable for the sprout inhibition of potatoes, did not cause significant inhibition of greening under any of the conditions of this experiment. Storage in enriched CO2 atmospheres inhibited the greening to the extent of 50% at 15% CO2, only upon prolonged illumination (12 days), while irradiation (40 Krad) was only effective after a short period (4 days) of illumination. Irradiation in the O–40 Krad range did not increase the inhibition caused by CO2. The inhibition of potato greening by irradiation was effective through a period of 5 weeks storage in the dark prior to illumination.

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