A study of the six isomeric xylenols (dimethyl phenols) as reagents for the colorimetric determination of the nitrate ion was undertaken.From nitration and absorption spectra studies it was shown that 3,4-xylenol (3,4-dimethyl phenol) was the best reagent. Methods for the colorimetric determination of inorganic nitrate and of nitric acid esters in the presence of stabilizers such as diphenylamine are described. They are based upon the fact that nitrates can be hydrolyzed by 80% sulfuric acid to yield nitric acid. The nitric acid liberated nitrates 3,4-xylenol, forming 6-nitro-3,4-xylenol which is steam-distilled from the reaction mixture and collected in an alkaline solution, forming the deeply colored sodium salt. This salt is capable of accurate colorimetric determination.The colored system, the nitration reaction, and the hydrolysis reactions are discussed. The recommended concentration range is from 0.10 to 0.35 mg. of nitrate nitrogen in 100 ml. of solution, using a cell depth of 1 cm. THISpaper deals with a study of the isomeric xylenols as reagents for the colorimetric determination of nitrate, and the colorimetric determination of nitrates and nitric acid esters. The method is based upon the fact that nitrates yield nitric acid on treatment with sulfuric acid. The nitric acid liberated is used to nitrate a xvlenol. The nitroxylenol is then steam-distilled from the reaction mixture, and the distillate is collected in an aqueous solution of sodium hydroxide, forming the deeply colored sodium salt of the nitroxylenol. This salt can be determined colorimetrically.A literature survey indicated that only 2,4-xylenol had been proposed (1, 2, 6, 9, 12, 14,15,18) as a reagent for nitrate analysis. APPARATUS AND REAGENTSApparatus. The optical density measurements were made with a Beckman Model DL" spectrophotometer. Absorption cells with a 0.998-cm. solution thickness were used.The all-glass steam distillation apparatus was made from 10mm. Pyrex tubing and consisted of a water-cooled condenser (Idem. jacket), and a 250-ml. round-bottomed flask. A standardtaper (24/40) joint connects the two.Reagents. 3,4-Xvlenol was obtained from the Eastman Kodak Company (Catalog No. 1155). 2,3-Xylenol was obtained through the courtesy of Lee I. Smith, University of Minnesota. 2,4-Xylenol, 3,5-xylenol, and 2,5-xylenol were obtained from the Reilly Tar and Chemical Corporation, Indianapolis, Ind.3,4-Xylenol reagent, 2 and 8% acetone solutions. Sulfuric acid (80 weight %). Mix 660 ml. of c.P. sulfuric acid

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In an investigation of the melting points of the disubstituted derivatives of benzene, it was noticed that a definite relationship does exist between the melting point of the isomers and their chemical constitution.The derivatives were placed in one of two classes on the basis of their structure. Class A, in which the disubstituted derivative contains one ortho-para orienting group (1, 2, 6); and one meta orienting group (1,2, 6); and Class B, in which the disubstituted derivative contains two ortho-para orienting or two meta orienting groups.Division of Groups. The substituent groups were divided into two classes, those that are meta orienting and those that are ortho-para orienting in character. Table I lists the various groups according to these properties.The Order of the Melting Points for the Disubstituted Derivatives of Benzene.The following rules are postulated from the data collected on the melting points of the disubstituted derivatives of benzene: Rule I. When the disubstituted benzene derivative contains one meta orienting group and one ortho-para orienting group, the order of the melting points for the isomers is: ortho < meta < para.Rule II. When the disubstituted benzene derivative contains only orthopara orienting or only meta orienting groups, the order of the melting points for the isomers is: meta < ortho < para.In Table II are listed the melting points of various disubstituted derivatives of benzene containing one ortho-para orienting group and one meta orienting group.

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Many factors contribute to water-line corrosion. The author briefly reviews the more common types, with emphasis on the problems confronting copper services.Although copper lines have performed well in many in stallations, in some, the results have been disasterous. Cop per, it was found, could be as subject to corrosion as iron or steel. Forms of CorrosionUniform attack. In uniform attack the water reacts with the metal to give a uniform depth of penetration of the metal over the entire surface. Acid solutions normally give rise to this type of attack. Water with a high content of dissolved salts and high electrical conductivity also give a uniform corrosion attack.A surface covered with a uniform deposit probably will un dergo a reasonably uniform type of attack. However, a deposit like calcium carbonate, which occurs from hard water will reduce the rate of attack to almost zero.Grooving. Grooving attack is the severe thinning of the pipe section in certain areas. The grooves are free from corros;ion products. Grooving is characteristic of acid-condensate at tack; that is, condensed steam that contains dissolved carbon dioxide (carbonic acid). Steel and copper condenser tubes are corroded by this grooving when large amounts of carbonates are present in the boiler-feed water. Severe thinning of the lower half of the horizontal returns is caused by the flow of acid condensate through the partially filled pipes. Grooving can also occur at a bimetal junction and will be largely con centrated on the anodic metal close to the line of contact Pitting. Pitting corrosion is the most serious form of localized attack because depth of penetration usually approxi mates the diameter of the corroded area.Pitting often results in the perforation of the pipe even though the amount of metal corrosion is very small. The size of pits may vary from shallow-hemispherical to pin-hole size in which the depth of penetration is much greater than the diameter.Corrosion by pitting is usually expressed in terms of the deepest pit, which makes more sense than expressing il in terms of distribution or of an average number of the deepest pits.The pitting phenomenon is not clearly understood. It starts with a small anodic area and a large cathodic area. The rate; of attack at this small anode is a function of the conductivity of the water and the cathodic and anodic polarization.Tuberculation. Mounds of corrosion product can form on the surface of metal from corrosion processes occurring on the surface; the mounds appear as tubercules, thus the name tuberculation.Mounds of corrosion product are associated with pitting and overlie anodic areas where localized attack is taking place. These mounds are often so large and numerous that frictional resistance to flow is increased, and the carrying capacity of the pipe is greatly reduced.These tubercules seen in steel or cast-iron water mains have a hard outer crust of brown hydrated ferric oxide and an inner layer of black magnetic or green rust. The crust physically separates the anodic area within ...

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